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Sample records for 7t multichannel phase

  1. Multichannel Phase and Power Detector

    NASA Technical Reports Server (NTRS)

    Li, Samuel; Lux, James; McMaster, Robert; Boas, Amy

    2006-01-01

    An electronic signal-processing system determines the phases of input signals arriving in multiple channels, relative to the phase of a reference signal with which the input signals are known to be coherent in both phase and frequency. The system also gives an estimate of the power levels of the input signals. A prototype of the system has four input channels that handle signals at a frequency of 9.5 MHz, but the basic principles of design and operation are extensible to other signal frequencies and greater numbers of channels. The prototype system consists mostly of three parts: An analog-to-digital-converter (ADC) board, which coherently digitizes the input signals in synchronism with the reference signal and performs some simple processing; A digital signal processor (DSP) in the form of a field-programmable gate array (FPGA) board, which performs most of the phase- and power-measurement computations on the digital samples generated by the ADC board; and A carrier board, which allows a personal computer to retrieve the phase and power data. The DSP contains four independent phase-only tracking loops, each of which tracks the phase of one of the preprocessed input signals relative to that of the reference signal (see figure). The phase values computed by these loops are averaged over intervals, the length of which is chosen to obtain output from the DSP at a desired rate. In addition, a simple sum of squares is computed for each channel as an estimate of the power of the signal in that channel. The relative phases and the power level estimates computed by the DSP could be used for diverse purposes in different settings. For example, if the input signals come from different elements of a phased-array antenna, the phases could be used as indications of the direction of arrival of a received signal and/or as feedback for electronic or mechanical beam steering. The power levels could be used as feedback for automatic gain control in preprocessing of incoming signals

  2. APHID: A Wideband, Multichannel Radiometer for Phase Delay Correction

    NASA Astrophysics Data System (ADS)

    Staguhn, J.; Harris, A. I.; Munday, L. G.; Woody, D. P.

    Atmospheric phase fluctuations of mm and sub-mm signals are predominantly caused by line of sight fluctuations in the amount of water vapor. Measurements of the line emission from tropospheric water vapor can be used to track and correct these fluctuations. We present model calculations which led to the design of a multichannel water vapor radiometer for phase correction of millimeter arrays. Our particular emphasis is on designing a phase correction scheme for mid-latitude sites (BIMA, OVRO), and for high-altitude sites. The instrument being implemented at OVRO and BIMA is a cooled double-sideband heterodyne receiver centered on the 22.2GHz water vapor line with a 0.5 - 4.0GHz IF. The back end is a 16 channel analog lag correlator similar to the WASP spectrometer (Harris et al 1998). We present two applications for the multichannel radiometer. A line fit to the observed spectra is expected to provide sufficient accuracy for mm phase correction with the 22 GHZ line. The radiometer can also be used for the determination of the vertical water vapor distribution from the observed line shape. We discuss how this information can be used to improve the accuracy of water vapor radiometers which have too few channels to observe the line shape, and for phase correction schemes which are based on a 183 GHz water line radiometer.

  3. High-resolution MRI of uveal melanoma using a microcoil phased array at 7 T.

    PubMed

    Beenakker, J W M; van Rijn, G A; Luyten, G P M; Webb, A G

    2013-12-01

    High-field MRI is a promising technique for the characterisation of ocular tumours, both in vivo and after enucleation. For in vivo imaging at 7 T, a dedicated three-element microcoil array was constructed as a high-sensitivity receive-only device. Using a dedicated blink/fixation protocol, high-resolution in vivo images could be acquired within 3 min in volunteers and patients with no requirement for post-acquisition image registration. Quantitative measures of axial length, aqueous depth and lens thickness in a healthy volunteer were found to agree well with standard ocular biometric techniques. In a patient with uveal melanoma, in vivo MRI gave excellent tumour/aqueous body contrast. Ex vivo imaging of the enucleated eye showed significant heterogeneity within the tumour.

  4. MRI phase changes in multiple sclerosis vs neuromyelitis optica lesions at 7T

    PubMed Central

    Sinnecker, Tim; Schumacher, Sophie; Mueller, Katharina; Pache, Florence; Dusek, Petr; Harms, Lutz; Ruprecht, Klemens; Nytrova, Petra; Chawla, Sanjeev; Niendorf, Thoralf; Kister, Ilya; Ge, Yulin; Wuerfel, Jens

    2016-01-01

    Objective: To characterize paramagnetic MRI phase signal abnormalities in neuromyelitis optica spectrum disorder (NMOSD) vs multiple sclerosis (MS) lesions in a cross-sectional study. Methods: Ten patients with NMOSD and 10 patients with relapsing-remitting MS underwent 7-tesla brain MRI including supratentorial T2*-weighted imaging and supratentorial susceptibility weighted imaging. Next, we analyzed intra- and perilesional paramagnetic phase changes on susceptibility weighted imaging filtered magnetic resonance phase images. Results: We frequently observed paramagnetic rim-like (75 of 232 lesions, 32%) or nodular (32 of 232 lesions, 14%) phase changes in MS lesions, but only rarely in NMOSD lesions (rim-like phase changes: 2 of 112 lesions, 2%, p < 0.001; nodular phase changes: 2 of 112 lesions, 2%, p < 0.001). Conclusions: Rim-like or nodular paramagnetic MRI phase changes are characteristic for MS lesions and not frequently detectable in NMOSD. Future prospective studies should ask whether these imaging findings can be used as a biomarker to distinguish between NMOSD- and MS-related brain lesions. PMID:27489865

  5. Image reconstruction from phased-array data based on multichannel blind deconvolution.

    PubMed

    She, Huajun; Chen, Rong-Rong; Liang, Dong; Chang, Yuchou; Ying, Leslie

    2015-11-01

    In this paper we consider image reconstruction from fully sampled multichannel phased array MRI data without knowledge of the coil sensitivities. To overcome the non-uniformity of the conventional sum-of-square reconstruction, a new framework based on multichannel blind deconvolution (MBD) is developed for joint estimation of the image function and the sensitivity functions in image domain. The proposed approach addresses the non-uniqueness of the MBD problem by exploiting the smoothness of both functions in the image domain through regularization. Results using simulation, phantom and in vivo experiments demonstrate that the reconstructions by the proposed algorithm are more uniform than those by the existing methods.

  6. Intraoperative multichannel audio-visual information recording and automatic surgical phase and incident detection.

    PubMed

    Suzuki, Takashi; Sakurai, Yasuo; Yoshimitsu, Kitaro; Nambu, Kyojiro; Muragaki, Yoshihiro; Iseki, Hiroshi

    2010-01-01

    Identification, analysis, and treatment of potential risk in surgical workflow are the key to decrease medical errors in operating room. For the automatic analysis of recorded surgical information, this study reports multichannel audio visual recording system, and its review and analysis system. Motion in operating room is quantified using video file size without motion tracking. Conversation among surgical staff is quantified using fast Fourier transformation and frequency filter without speech recognition. The results suggested the progression phase of surgical procedure.

  7. Design of non-selective refocusing pulses with phase-free rotation axis by gradient ascent pulse engineering algorithm in parallel transmission at 7 T

    NASA Astrophysics Data System (ADS)

    Massire, Aurélien; Cloos, Martijn A.; Vignaud, Alexandre; Le Bihan, Denis; Amadon, Alexis; Boulant, Nicolas

    2013-05-01

    At ultra-high magnetic field (⩾7 T), B1 and ΔB0 non-uniformities cause undesired inhomogeneities in image signal and contrast. Tailored radiofrequency pulses exploiting parallel transmission have been shown to mitigate these phenomena. However, the design of large flip angle excitations, a prerequisite for many clinical applications, remains challenging due the non-linearity of the Bloch equation. In this work, we explore the potential of gradient ascent pulse engineering to design non-selective spin-echo refocusing pulses that simultaneously mitigate severe B1 and ΔB0 non-uniformities. The originality of the method lays in the optimization of the rotation matrices themselves as opposed to magnetization states. Consequently, the commonly used linear class of large tip angle approximation can be eliminated from the optimization procedure. This approach, combined with optimal control, provides additional degrees of freedom by relaxing the phase constraint on the rotation axis, and allows the derivative of the performance criterion to be found analytically. The method was experimentally validated on an 8-channel transmit array at 7 T, using a water phantom with B1 and ΔB0 inhomogeneities similar to those encountered in the human brain. For the first time in MRI, the rotation matrix itself on every voxel was measured by using Quantum Process Tomography. The results are complemented with a series of spin-echo measurements comparing the proposed method against commonly used alternatives. Both experiments confirm very good performance, while simultaneously maintaining a low energy deposition and pulse duration compared to well-known adiabatic solutions.

  8. A Phase 1 Study of 7-t-butyldimethylsilyl-10-hydroxycamptothecin (AR-67) in Adult Patients with Refractory or Metastatic Solid Malignancies

    PubMed Central

    Arnold, Susanne M.; Rinehart, John J.; Tsakalozou, Eleftheria; Eckardt, John R.; Fields, Scott Z.; Shelton, Brent J.; DeSimone, Philip A.; Kee, Bryan K.; Moscow, Jeffrey A.; Leggas, Markos

    2009-01-01

    Purpose AR-67 is a novel third generation camptothecin selected for development based on the blood stability of its pharmacologically active lactone form and high potency in preclinical models. Here we report the initial phase I experience with intravenous AR-67 in adults with refractory solid tumors. Experimental Design and Methods AR-67 was infused over 1 hour daily × 5, every 21-days, using an accelerated titration trial design. Plasma was collected on the 1st and 4th day of cycle 1 to determine pharmacokinetic parameters. Results Twenty six patients were treated at 9 dosage levels (1.2–12.4mg/m2/day). Dose limiting toxicities (DLTs) were observed in 5 patients and consisted of grade 4 febrile neutropenia, grade 3 fatigue, and grade 4 thrombocytopenia. Common toxicities included: leukopenia (23%), thrombocytopenia (15.4%), fatigue (15.4%), neutropenia (11.5%), and anemia (11.5%). No diarrhea was observed. The maximum tolerated dosage (MTD) was 7.5 mg/m2/day. The lactone form was the predominant species in plasma (>87% of AUC) at all dosages. No drug accumulation was observed on day 4. Clearance was constant with increasing dosage and hematologic toxicities correlated with exposure (p<0.001). A prolonged partial response was observed in one subject with non-small cell lung cancer (NSCLC). Stable disease was noted in patients with small cell lung cancer (SCLC), NSCLC, and duodenal cancer. Conclusions AR-67 is a novel, blood stable camptothecin with a predictable toxicity profile and linear pharmacokinetics. The recommended phase II dosage is 7.5mg/m2/day ×5 q 21 days. PMID:20068096

  9. Equalization enhanced phase noise in Nyquist-spaced superchannel transmission systems using multi-channel digital back-propagation.

    PubMed

    Xu, Tianhua; Liga, Gabriele; Lavery, Domaniç; Thomsen, Benn C; Savory, Seb J; Killey, Robert I; Bayvel, Polina

    2015-09-14

    Superchannel transmission spaced at the symbol rate, known as Nyquist spacing, has been demonstrated for effectively maximizing the optical communication channel capacity and spectral efficiency. However, the achievable capacity and reach of transmission systems using advanced modulation formats are affected by fibre nonlinearities and equalization enhanced phase noise (EEPN). Fibre nonlinearities can be effectively compensated using digital back-propagation (DBP). However EEPN which arises from the interaction between laser phase noise and dispersion cannot be efficiently mitigated, and can significantly degrade the performance of transmission systems. Here we report the first investigation of the origin and the impact of EEPN in Nyquist-spaced superchannel system, employing electronic dispersion compensation (EDC) and multi-channel DBP (MC-DBP). Analysis was carried out in a Nyquist-spaced 9-channel 32-Gbaud DP-64QAM transmission system. Results confirm that EEPN significantly degrades the performance of all sub-channels of the superchannel system and that the distortions are more severe for the outer sub-channels, both using EDC and MC-DBP. It is also found that the origin of EEPN depends on the relative position between the carrier phase recovery module and the EDC (or MC-DBP) module. Considering EEPN, diverse coding techniques and modulation formats have to be applied for optimizing different sub-channels in superchannel systems.

  10. Equalization enhanced phase noise in Nyquist-spaced superchannel transmission systems using multi-channel digital back-propagation

    PubMed Central

    Xu, Tianhua; Liga, Gabriele; Lavery, Domaniç; Thomsen, Benn C.; Savory, Seb J.; Killey, Robert I.; Bayvel, Polina

    2015-01-01

    Superchannel transmission spaced at the symbol rate, known as Nyquist spacing, has been demonstrated for effectively maximizing the optical communication channel capacity and spectral efficiency. However, the achievable capacity and reach of transmission systems using advanced modulation formats are affected by fibre nonlinearities and equalization enhanced phase noise (EEPN). Fibre nonlinearities can be effectively compensated using digital back-propagation (DBP). However EEPN which arises from the interaction between laser phase noise and dispersion cannot be efficiently mitigated, and can significantly degrade the performance of transmission systems. Here we report the first investigation of the origin and the impact of EEPN in Nyquist-spaced superchannel system, employing electronic dispersion compensation (EDC) and multi-channel DBP (MC-DBP). Analysis was carried out in a Nyquist-spaced 9-channel 32-Gbaud DP-64QAM transmission system. Results confirm that EEPN significantly degrades the performance of all sub-channels of the superchannel system and that the distortions are more severe for the outer sub-channels, both using EDC and MC-DBP. It is also found that the origin of EEPN depends on the relative position between the carrier phase recovery module and the EDC (or MC-DBP) module. Considering EEPN, diverse coding techniques and modulation formats have to be applied for optimizing different sub-channels in superchannel systems. PMID:26365422

  11. Selecting the optimal anti-aliasing filter for multichannel biosignal acquisition intended for inter-signal phase shift analysis.

    PubMed

    Keresnyei, Róbert; Megyeri, Péter; Zidarics, Zoltán; Hejjel, László

    2015-01-01

    The availability of microcomputer-based portable devices facilitates the high-volume multichannel biosignal acquisition and the analysis of their instantaneous oscillations and inter-signal temporal correlations. These new, non-invasively obtained parameters can have considerable prognostic or diagnostic roles. The present study investigates the inherent signal delay of the obligatory anti-aliasing filters. One cycle of each of the 8 electrocardiogram (ECG) and 4 photoplethysmogram signals from healthy volunteers or artificially synthesised series were passed through 100-80-60-40-20 Hz 2-4-6-8th order Bessel and Butterworth filters digitally synthesized by bilinear transformation, that resulted in a negligible error in signal delay compared to the mathematical model of the impulse- and step responses of the filters. The investigated filters have as diverse a signal delay as 2-46 ms depending on the filter parameters and the signal slew rate, which is difficult to predict in biological systems and thus difficult to compensate for. Its magnitude can be comparable to the examined phase shifts, deteriorating the accuracy of the measurement. As a conclusion, identical or very similar anti-aliasing filters with lower orders and higher corner frequencies, oversampling, and digital low pass filtering are recommended for biosignal acquisition intended for inter-signal phase shift analysis. PMID:25514627

  12. Surface wave phase-velocity tomography based on multichannel cross-correlation

    NASA Astrophysics Data System (ADS)

    Jin, Ge; Gaherty, James B.

    2015-06-01

    We have developed a new method to retrieve seismic surface wave phase velocity using dense seismic arrays. The method measures phase variations between nearby stations based on waveform cross-correlation. The coherence in waveforms between adjacent stations results in highly precise relative phase estimates. Frequency-dependent phase variations are then inverted for spatial variations in apparent phase velocity via the Eikonal equation. Frequency-dependent surface wave amplitudes measured on individual stations are used to correct the apparent phase velocity to account for multipathing via the Helmholtz equation. By using coherence and other data selection criteria, we construct an automated system that retrieves structural phase-velocity maps directly from raw seismic waveforms for individual earthquakes without human intervention. The system is applied to broad-band seismic data from over 800 events recorded on EarthScope's USArray from 2006 to 2014, systematically building up Rayleigh-wave phase-velocity maps between the periods of 20 and 100 s for the entire continental United States. At the highest frequencies, the resulting maps are highly correlated with phase-velocity maps derived from ambient noise tomography. At all frequencies, we observe a significant contrast in Rayleigh-wave phase velocity between the tectonically active western US and the stable eastern US, with the phase velocity variations in the western US being 1-2 times greater. The Love wave phase-velocity maps are also calculated. We find that overtone contamination may produce systemic bias for the Love-wave phase-velocity measurements.

  13. Single-subject fMRI mapping at 7 T of the representation of fingertips in S1: a comparison of event-related and phase-encoding designs.

    PubMed

    Besle, Julien; Sánchez-Panchuelo, Rosa-Maria; Bowtell, Richard; Francis, Susan; Schluppeck, Denis

    2013-05-01

    A desirable goal of functional MRI (fMRI), both clinically and for basic research, is to produce detailed maps of cortical function in individual subjects. Single-subject mapping of the somatotopic hand representation in the human primary somatosensory cortex (S1) has been performed using both phase-encoding and block/event-related designs. Here, we review the theoretical strengths and limits of each method and empirically compare high-resolution (1.5 mm isotropic) somatotopic maps obtained using fMRI at ultrahigh magnetic field (7 T) with phase-encoding and event-related designs in six subjects in response to vibrotactile stimulation of the five fingertips. Results show that the phase-encoding design is more efficient than the event-related design for mapping fingertip-specific responses and in particular allows us to describe a new additional somatotopic representation of fingertips on the precentral gyrus. However, with sufficient data, both designs yield very similar fingertip-specific maps in S1, which confirms that the assumption of local representational continuity underlying phase-encoding designs is largely valid at the level of the fingertips in S1. In addition, it is shown that the event-related design allows the mapping of overlapping cortical representations that are difficult to estimate using the phase-encoding design. The event-related data show a complex pattern of overlapping cortical representations for different fingertips within S1 and demonstrate that regions of S1 responding to several adjacent fingertips can incorrectly be identified as responding preferentially to one fingertip in the phase-encoding data.

  14. Single-subject fMRI mapping at 7 T of the representation of fingertips in S1: a comparison of event-related and phase-encoding designs

    PubMed Central

    Sánchez-Panchuelo, Rosa-Maria; Bowtell, Richard; Francis, Susan; Schluppeck, Denis

    2013-01-01

    A desirable goal of functional MRI (fMRI), both clinically and for basic research, is to produce detailed maps of cortical function in individual subjects. Single-subject mapping of the somatotopic hand representation in the human primary somatosensory cortex (S1) has been performed using both phase-encoding and block/event-related designs. Here, we review the theoretical strengths and limits of each method and empirically compare high-resolution (1.5 mm isotropic) somatotopic maps obtained using fMRI at ultrahigh magnetic field (7 T) with phase-encoding and event-related designs in six subjects in response to vibrotactile stimulation of the five fingertips. Results show that the phase-encoding design is more efficient than the event-related design for mapping fingertip-specific responses and in particular allows us to describe a new additional somatotopic representation of fingertips on the precentral gyrus. However, with sufficient data, both designs yield very similar fingertip-specific maps in S1, which confirms that the assumption of local representational continuity underlying phase-encoding designs is largely valid at the level of the fingertips in S1. In addition, it is shown that the event-related design allows the mapping of overlapping cortical representations that are difficult to estimate using the phase-encoding design. The event-related data show a complex pattern of overlapping cortical representations for different fingertips within S1 and demonstrate that regions of S1 responding to several adjacent fingertips can incorrectly be identified as responding preferentially to one fingertip in the phase-encoding data. PMID:23427300

  15. Investigation of multichannel phased array performance for fetal MR imaging on 1.5T clinical MR system

    PubMed Central

    Li, Ye; Pang, Yong; Vigneron, Daniel; Glenn, Orit; Xu, Duan; Zhang, Xiaoliang

    2011-01-01

    Fetal MRI on 1.5T clinical scanner has been increasingly becoming a powerful imaging tool for studying fetal brain abnormalities in vivo. Due to limited availability of dedicated fetal phased arrays, commercial torso or cardiac phased arrays are routinely used for fetal scans, which are unable to provide optimized SNR and parallel imaging performance with a small number coil elements, and insufficient coverage and filling factor. This poses a demand for the investigation and development of dedicated and efficient radiofrequency (RF) hardware to improve fetal imaging. In this work, an investigational approach to simulate the performance of multichannel flexible phased arrays is proposed to find a better solution to fetal MR imaging. A 32 channel fetal array is presented to increase coil sensitivity, coverage and parallel imaging performance. The electromagnetic field distribution of each element of the fetal array is numerically simulated by using finite-difference time-domain (FDTD) method. The array performance, including B1 coverage, parallel reconstructed images and artifact power, is then theoretically calculated and compared with the torso array. Study results show that the proposed array is capable of increasing B1 field strength as well as sensitivity homogeneity in the entire area of uterus. This would ensure high quality imaging regardless of the location of the fetus in the uterus. In addition, the paralleling imaging performance of the proposed fetal array is validated by using artifact power comparison with torso array. These results demonstrate the feasibility of the 32 channel flexible array for fetal MR imaging at 1.5T. PMID:22408747

  16. A multi-channel image reconstruction method for grating-based X-ray phase-contrast computed tomography

    NASA Astrophysics Data System (ADS)

    Xu, Qiaofeng; Sawatzky, Alex; Anastasio, Mark A.

    2014-03-01

    In this work, we report on the development of an advanced multi-channel (MC) image reconstruction algorithm for grating-based X-ray phase-contrast computed tomography (GB-XPCT). The MC reconstruction method we have developed operates by concurrently, rather than independently as is done conventionally, reconstructing tomographic images of the three object properties (absorption, small-angle scattering, refractive index). By jointly estimating the object properties by use of an appropriately defined penalized weighted least squares (PWLS) estimator, the 2nd order statistical properties of the object property sinograms, including correlations between them, can be fully exploited to improve the variance vs. resolution tradeoff of the reconstructed images as compared to existing methods. Channel-independent regularization strategies are proposed. To solve the MC reconstruction problem, we developed an advanced algorithm based on the proximal point algorithm and the augmented Lagrangian method. By use of experimental and computer-simulation data, we demonstrate that by exploiting inter-channel noise correlations, the MC reconstruction method can improve image quality in GB-XPCT.

  17. A portable and autonomous multichannel fluorescence detector for on-line and in situ explosive detection in aqueous phase.

    PubMed

    Xin, Yunhong; Wang, Qi; Liu, Taihong; Wang, Lingling; Li, Jia; Fang, Yu

    2012-11-21

    A multichannel fluorescence detector used to detect nitroaromatic explosives in aqueous phase has been developed, which is composed of a five-channel sample-sensor unit, a measurement and control unit, a microcontroller, and a communication unit. The characteristics of the detector as developed are mainly embedded in the sensor unit, and each sensor consists of a fluorescent sensing film, a light emitting diode (LED), a multi-pixel photon counter (MPPC), and an optical module with special bandpass optical filters. Due to the high sensitivity of the sensing film, the small size and low cost of LED and MPPC, the developed detector not only has a better detecting performance and small size, but also has a very low cost - it is an alternative to the device made with an expensive high power lamp and photomultiplier tube. The wavelengths of the five sensors covered extend from the upper UV through the visible spectrum, 370-640 nm, and thereby it possesses the potential to detect a variety of explosives and other hazardous materials in aqueous phase. An additional function of the detector is its ability to function via a wireless network, by which the data recorded by the detector can be sent to the host computer, and at the same time the instructions can be sent to the detector from the host computer. By means of the powerful computing ability of the host computer, and utilizing the classical principal component analysis (PCA) algorithm, effective classification of the analytes is achieved. Furthermore, the detector has been tested and evaluated using NB, PA, TNT and DNT as the analytes, and toluene, benzene, methanol and ethanol as interferent compounds (concentration various from 10 and 60 μM). It has been shown that the detector can detect the four nitroaromatics with high sensitivity and selectivity.

  18. Density of states at disorder-induced phase transitions in a multichannel Majorana wire

    NASA Astrophysics Data System (ADS)

    Rieder, Maria-Theresa; Brouwer, Piet W.

    2014-11-01

    An N -channel spinless p -wave superconducting wire is known to go through a series of N topological phase transitions upon increasing the disorder strength. Here, we show that at each of those transitions the density of states shows a Dyson singularity ν (ɛ ) ∝ɛ-1|lnɛ| -3 , whereas ν (ɛ ) ∝ɛ|α |-1 has a power-law singularity for small energies ɛ away from the critical points. Using the concept of "superuniversality" [Gruzberg et al., Phys. Rev. B 71, 245124 (2005), 10.1103/PhysRevB.71.245124], we are able to relate the exponent α to the wire's transport properties at zero energy and, hence, to the mean free path l and the superconducting coherence length ξ .

  19. Phase Structure of the T-matrix and Multichannel Unitary Isobar Model

    NASA Astrophysics Data System (ADS)

    Razavi, S.; Nakayama, K.

    2015-04-01

    By exploiting the full phase structure of the meson-baryon coupled channels reaction amplitude-here including also the photon-baryon channel-an isobar model is constructed which fulfills automatically the unitarity and analyticity conditions of the S-matrix, in addition to gauge invariance in the case of photoproduction. In particular, it is shown that the unitarity of the (resonance) pole amplitude arises from the dressing mechanism inherent in the basic T-matrix equation, requiring no extra unitarity condition on the pole amplitude as is the case in earlier works on isobar models. As an example, the present model is applied in the description of the meson-nucleon reactions including the πN , ηN , σN , ρN and πΔ channels. The latter three account effectively for the ππN channel. FFE-COSY Grant No. 41788390.

  20. MULTICHANNEL ANALYZER

    DOEpatents

    Kelley, G.G.

    1959-11-10

    A multichannel pulse analyzer having several window amplifiers, each amplifier serving one group of channels, with a single fast pulse-lengthener and a single novel interrogation circuit serving all channels is described. A pulse followed too closely timewise by another pulse is disregarded by the interrogation circuit to prevent errors due to pulse pileup. The window amplifiers are connected to the pulse lengthener output, rather than the linear amplifier output, so need not have the fast response characteristic formerly required.

  1. Phase control of multichannel molecular high-order harmonic generation by the asymmetric diatomic molecule HeH{sup 2+} in two-color laser fields

    SciTech Connect

    Bian Xuebin; Bandrauk, Andre D.

    2011-02-15

    Multichannel molecular high-order harmonic generation (MHOHG) from the asymmetric diatomic molecule HeH{sup 2+} in two-color laser fields is investigated from numerical simulation of the corresponding time-dependent Schroedinger equation (TDSE). It is found that the laser-induced electron transfer (LIET) plays a crucial role in MHOHG, which leads to the multichannel harmonic generation from the ground and long-lifetime excited states. LIET is sensitive to the phase differences of the two-color laser pulses, which can be used to control the enhanced excitation (EE) and enhanced ionization (EI) of the system. Both EE and EI have a strong influence on the overall intensity of the MHOHG spectrum, and there may be four orders of magnitude difference in the MHOHG intensity between the enhanced and suppressed cases. In addition, owing to the asymmetry of the two-color laser fields and the recombination of electron with the neighboring ion, multiple cutoff energies are observed. The mechanism of these effects are confirmed by classical simulations.

  2. Binary phase shift keying on orthogonal carriers for multi-channel CO2 absorption measurements in the presence of thin clouds.

    PubMed

    Campbell, Joel F; Lin, Bing; Nehrir, Amin R; Harrison, F Wallace; Obland, Michael D

    2014-10-20

    A new modulation technique for Continuous Wave (CW) Lidar is presented based on Binary Phase Shift Keying (BPSK) using orthogonal carriers closely spaced in frequency, modulated by Maximum Length (ML) sequences, which have a theoretical autocorrelation function with no sidelobes. This makes it possible to conduct multi-channel atmospheric differential absorption measurements in the presence of thin clouds without the need for further processing to remove errors caused by sidelobe interference while sharing the same modulation bandwidth. Flight tests were performed and data were collected using both BPSK and linear swept frequency modulation. This research shows there is minimal or no sidelobe interference in the presence of thin clouds for BPSK compared to linear swept frequency with significant sidelobe levels. Comparisons between of CO(2) optical depth Signal to Noise (SNR) between the BPSK and linear swept frequency cases indicate a 21% drop in SNR for BPSK experimentally using the instrument under consideration.

  3. Design of a parallel transmit head coil at 7T with magnetic wall distributed filters.

    PubMed

    Connell, Ian R O; Gilbert, Kyle M; Abou-Khousa, Mohamed A; Menon, Ravi S

    2015-04-01

    Ultra-high field magnetic resonance imaging (MRI) scanners ( ≥ 7T) require radio-frequency (RF) coils to operate in the range of the electromagnetic spectrum where the effective wavelength in the tissue approaches the patient dimensions. Multi-channel transmit arrays, driven in parallel, have been developed to increase the transmit field (B1(+)) uniformity in this wavelength regime. However, the closely packed array elements interact through mutual coupling. This paper expands on the ability of a distributed planar filter (the "magnetic wall") to decouple individual elements in an entire array. A transmit RF coil suitable for neuroimaging at 7T was constructed. The transmit coil, composed of 10 individual surface coil elements, was decoupled with magnetic walls. A separate receive coil array was used for signal reception. The hardware and imaging performance of the transmit coil was validated with electromagnetic simulation, bench-top measurements, and in vivo MRI experiments. Analysis and measurements confirmed that the magnetic wall decoupling method provides high isolation between transmit channels, while minimally affecting the B1(+) field profiles. Electromagnetic simulations confirmed that the decoupling method did not correlate to local specific absorption rate (SAR) "hot spots" or increase local-to-global SAR fractions in comparison to previously reported 7T multi-channel transmit arrays employing different decoupling methods.

  4. Complex B1 Mapping and Electrical Properties Imaging of the Human Brain using a 16-channel Transceiver Coil at 7T

    PubMed Central

    Zhang, Xiaotong; Van de Moortele, Pierre-Francois; Schmitter, Sebastian; He, Bin

    2012-01-01

    The electric properties (EPs) of biological tissue provide important diagnostic information within radio and microwave frequencies, and also play an important role in specific absorption rate (SAR) calculation which is a major safety concern at ultrahigh field (UHF). The recently proposed electrical properties tomography (EPT) technique aims to reconstruct EPs in biological tissues based on B1 measurement. However, for individual coil element in multi-channel transceiver coil which is increasingly utilized at UHF, current B1-mapping techniques could not provide adequate information (magnitude and absolute phase) of complex transmit and receive B1 which are essential for EPT, electric field, and quantitative SAR assessment. In this study, using a 16-channel transceiver coil at 7T, based on hybrid B1-mapping techniques within the human brain, a complex B1-mapping method has been developed, and in-vivo EPs imaging of the human brain has been demonstrated by applying a logarithm-based inverse algorithm. Computer simulation studies as well as phantom and human experiments have been conducted at 7T. The average bias and standard deviation for reconstructed conductivity in vivo were 28% and 67%, and 10% and 43% for relative permittivity, respectively. The present results suggest the feasibility and reliability of proposed complex B1-mapping technique and EPs reconstruction method. PMID:22692921

  5. Highly time-resolved evaluation technique of instantaneous amplitude and phase difference using analytic signals for multi-channel diagnostics.

    PubMed

    Ohshima, S; Kobayashi, S; Yamamoto, S; Nagasaki, K; Mizuuchi, T; Kado, S; Okada, H; Minami, T; Lee, H Y; Zang, L; Kenmochi, N; Kasajima, K; Ohtani, Y; Shi, N; Nagae, Y; Konoshima, S; Sano, F

    2014-11-01

    A fluctuation analysis technique using analytic signals is proposed. Analytic signals are suitable to characterize a single mode with time-dependent amplitude and frequency, such as an MHD mode observed in fusion plasmas since the technique can evaluate amplitude and frequency at a specific moment without limitations of temporal and frequency resolutions, which is problematic in Fourier-based analyses. Moreover, a concept of instantaneous phase difference is newly introduced, and error of the evaluated phase difference and its error reduction techniques using conditional/ensemble averaging are discussed. These techniques are applied to experimental data of the beam emission spectroscopic measurement in the Heliotron J device, which demonstrates that the technique can describe nonlinear evolution of MHD instabilities. This technique is widely applicable to other diagnostics having necessity to evaluate phase difference.

  6. Multichannel analysis of surface waves

    USGS Publications Warehouse

    Park, C.B.; Miller, R.D.; Xia, J.

    1999-01-01

    The frequency-dependent properties of Rayleigh-type surface waves can be utilized for imaging and characterizing the shallow subsurface. Most surface-wave analysis relies on the accurate calculation of phase velocities for the horizontally traveling fundamental-mode Rayleigh wave acquired by stepping out a pair of receivers at intervals based on calculated ground roll wavelengths. Interference by coherent source-generated noise inhibits the reliability of shear-wave velocities determined through inversion of the whole wave field. Among these nonplanar, nonfundamental-mode Rayleigh waves (noise) are body waves, scattered and nonsource-generated surface waves, and higher-mode surface waves. The degree to which each of these types of noise contaminates the dispersion curve and, ultimately, the inverted shear-wave velocity profile is dependent on frequency as well as distance from the source. Multichannel recording permits effective identification and isolation of noise according to distinctive trace-to-trace coherency in arrival time and amplitude. An added advantage is the speed and redundancy of the measurement process. Decomposition of a multichannel record into a time variable-frequency format, similar to an uncorrelated Vibroseis record, permits analysis and display of each frequency component in a unique and continuous format. Coherent noise contamination can then be examined and its effects appraised in both frequency and offset space. Separation of frequency components permits real-time maximization of the S/N ratio during acquisition and subsequent processing steps. Linear separation of each ground roll frequency component allows calculation of phase velocities by simply measuring the linear slope of each frequency component. Breaks in coherent surface-wave arrivals, observable on the decomposed record, can be compensated for during acquisition and processing. Multichannel recording permits single-measurement surveying of a broad depth range, high levels of

  7. Joint enhancement of multichannel SAR data

    NASA Astrophysics Data System (ADS)

    Ramakrishnan, Naveen; Ertin, Emre; Moses, Randolph L.

    2007-04-01

    In this paper we consider the problem of joint enhancement of multichannel Synthetic Aperture Radar (SAR) data. Previous work by Cetin and Karl introduced nonquadratic regularization methods for image enhancement using sparsity enforcing penalty terms. For multichannel data, independent enhancement of each channel is shown to degrade the relative phase information across channels that is useful for 3D reconstruction. We thus propose a method for joint enhancement of multichannel SAR data with joint sparsity constraints. We develop both a gradient-based and a Lagrange-Newton-based method for solving the joint reconstruction problem, and demonstrate the performance of the proposed methods on IFSAR height extraction problem from multi-elevation data.

  8. Magnetic resonance imaging of the canine brain at 7 T.

    PubMed

    Kang, Byeong-Teck; Ko, Ki-Jin; Jang, Dong-Pyo; Han, Jae-Yong; Lim, Chae-Young; Park, Chul; Yoo, Jong-Hyun; Kim, Ju-Won; Jung, Dong-In; Kim, Young-Bo; Woo, Eung-Je; Cho, Zang-Hee; Park, Hee-Myung

    2009-01-01

    The purpose of this study was to describe relevant canine brain structures as seen on T2-weighted images following magnetic resonance (MR) imaging at 7 T and to compare the results with imaging at 1.5 T. Imaging was performed on five healthy laboratory beagle dogs using 1.5 and 7 T clinical scanners. At 1.5 T, spin echo images were acquired, while gradient echo images were acquired at 3 T. Image quality and conspicuity of anatomic structures were evaluated qualitatively by direct comparison of the images obtained from the two different magnetic fields. The signal-to-nose ratio (SNR) and contrast-to-noise ratio (CNR) were calculated and compared between 1.5 and 7 T. The T2-weighted images at 7 T provided good spatial and contrast resolution for the identification of clinically relevant brain anatomy; these images provided better delineation and conspicuity of the brain stem and cerebellar structures, which were difficult to unequivocally identify at 1.5 T. However, frontal and parietal lobe and the trigeminal nerve were difficult to identify at 7 T due to susceptibility artifact. The SNR and CNR of the images at 7 T were significantly increased up to 318% and 715% compared with the 1.5 T images. If some disadvantages of 7 T imaging, such as susceptibility artifacts, technical difficulties, and high cost, can be improved, 7 T clinical MR imaging could provide a good experimental and diagnostic tool for the evaluation of canine brain disorders.

  9. Frequency Mapping of Rat Spinal Cord at 7T

    NASA Astrophysics Data System (ADS)

    Chen, Evan; Rauscher, Alexander; Kozlowski, Piotr; Yung, Andrew

    2012-10-01

    The spinal cord is an integral part of the nervous system responsible for sensory, motor, and reflex control crucial to all bodily function. Due to its non-invasive nature, MRI is well matched for characterizing and imaging of spinal cord, and is used extensively for clinical applications. Recent developments in magnetic resonance imaging (MRI) at high field (7T) using phase represents a new approach of characterizing spinal cord myelin. Theory suggests that microstructure differences in myelinated white matter (WM) and non-myelinated gray matter (GM) affect MR phase, measurable frequency shifts. Data from pilot experiments using a multi-gradient echo (MGE) sequence to image rat spinal cords placed parallel to main magnetic field B0 has shown frequency shifts between not only between WM and GM, but also between specific WM tracts of the dorsal column, including the fasciculus gracilis, fasciculus cuneatus, and corticospinal tract. Using MGE, frequency maps at multiple echo times (TE) between 4ms and 22ms show a non-linear relationship between WM frequency, contrary to what was previously expected. These results demonstrate the effectiveness of MGE in revealing new information about spinal cord tissue microstructure, and lays important groundwork for in-vivo and human studies.

  10. List mode multichannel analyzer

    SciTech Connect

    Archer, Daniel E.; Luke, S. John; Mauger, G. Joseph; Riot, Vincent J.; Knapp, David A.

    2007-08-07

    A digital list mode multichannel analyzer (MCA) built around a programmable FPGA device for onboard data analysis and on-the-fly modification of system detection/operating parameters, and capable of collecting and processing data in very small time bins (<1 millisecond) when used in histogramming mode, or in list mode as a list mode MCA.

  11. Multichannel Human Body Communication

    NASA Astrophysics Data System (ADS)

    Przystup, Piotr; Bujnowski, Adam; Wtorek, Jerzy

    2016-01-01

    Human Body Communication is an attractive alternative for traditional wireless communication (Bluetooth, ZigBee) in case of Body Sensor Networks. Low power, high data rates and data security makes it ideal solution for medical applications. In this paper, signal attenuation for different frequencies, using FR4 electrodes, has been investigated. Performance of single and multichannel transmission with frequency modulation of analog signal has been tested. Experiment results show that HBC is a feasible solution for transmitting data between BSN nodes.

  12. Miniature multichannel biotelemeter system

    NASA Technical Reports Server (NTRS)

    Carraway, J. B.; Sumida, J. T. (Inventor)

    1974-01-01

    A miniature multichannel biotelemeter system is described. The system includes a transmitter where signals from different sources are sampled to produce a wavetrain of pulses. The transmitter also separates signals by sync pulses. The pulses amplitude modulate a radio frequency carrier which is received at a receiver unit. There the sync pulses are detected by a demultiplexer which routes the pulses from each different source to a separate output channel where the pulses are used to reconstruct the signals from the particular source.

  13. Marine Multichannel Seismology Workshop

    NASA Astrophysics Data System (ADS)

    Detrick, Bob

    1984-04-01

    The multichannel seismic (MCS) reflection technique, developed by the oil industry for petroleum exploration in sedimentary basins, has proven to be a powerful tool for imaging subsurface geology in a wide variety of tectonic settings at a scale suitable for detailed investigations of geological structures and processes. In the ocean basins, MCS studies have provided new insight into the tectonic history of rifted and convergent continental margins, the structure of the oceanic crust and midocean ridges, and the sedimentation history and paleoceanography of deep ocean basins. MCS techniques have thus developed into an important tool for marine geological and geophysical research.The National Science Foundation recently sponsored a Workshop on the Future of Academic Marine Multichannel Seismology in the United States, held in Boulder, Colo., on March 19-20, 1984, to review the current state of marine academic MCS in the United States and to make recommendations on the facilities and funding required to meet future scientific needs. The workshop, which was convened by Brian T.R. Lewis of the University of Washington, included 19 scientists representing the major U.S. oceanographic institutions with interests in marine seismic work. This article summarizes the major recommendations developed at this workshop, which have been included in a more comprehensive report entitled ‘A National Plan for Marine Multichannel Seismology,’ which has been submitted to the National Science Foundation for future publication.

  14. Enhancement of coupled multichannel images using sparsity constraints.

    PubMed

    Ramakrishnan, Naveen; Ertin, Emre; Moses, Randolph L

    2010-08-01

    We consider the problem of joint enhancement of multichannel images with pixel based constraints on the multichannel data. Previous work by Cetin and Karl introduced nonquadratic regularization methods for SAR image enhancement using sparsity enforcing penalty terms. We formulate an optimization problem that jointly enhances complex-valued multichannel images while preserving the cross-channel information, which we include as constraints tying the multichannel images together. We pose this problem as a joint optimization problem with constraints. We first reformulate it as an equivalent (unconstrained) dual problem and develop a numerically-efficient method for solving it. We develop the Dual Descent method, which has low complexity, for solving the joint optimization problem. The algorithm is applied to both an interferometric synthetic aperture radar (IFSAR) problem, in which the relative phase between two complex-valued images indicate height, and to a synthetic multimodal medical image example. PMID:20236892

  15. Fractional channel multichannel analyzer

    DOEpatents

    Brackenbush, Larry W.; Anderson, Gordon A.

    1994-01-01

    A multichannel analyzer incorporating the features of the present invention obtains the effect of fractional channels thus greatly reducing the number of actual channels necessary to record complex line spectra. This is accomplished by using an analog-to-digital converter in the asynscronous mode, i.e., the gate pulse from the pulse height-to-pulse width converter is not synchronized with the signal from a clock oscillator. This saves power and reduces the number of components required on the board to achieve the effect of radically expanding the number of channels without changing the circuit board.

  16. Multichannel interval timer (MINT)

    SciTech Connect

    Kimball, K.B.

    1982-06-01

    A prototype Multichannel INterval Timer (MINT) has been built for measuring signal Time of Arrival (TOA) from sensors placed in blast environments. The MINT is intended to reduce the space, equipment costs, and data reduction efforts associated with traditional analog TOA recording methods, making it more practical to field the large arrays of TOA sensors required to characterize blast environments. This document describes the MINT design features, provides the information required for installing and operating the system, and presents proposed improvements for the next generation system.

  17. Software Configurable Multichannel Transceiver

    NASA Technical Reports Server (NTRS)

    Freudinger, Lawrence C.; Cornelius, Harold; Hickling, Ron; Brooks, Walter

    2009-01-01

    Emerging test instrumentation and test scenarios increasingly require network communication to manage complexity. Adapting wireless communication infrastructure to accommodate challenging testing needs can benefit from reconfigurable radio technology. A fundamental requirement for a software-definable radio system is independence from carrier frequencies, one of the radio components that to date has seen only limited progress toward programmability. This paper overviews an ongoing project to validate the viability of a promising chipset that performs conversion of radio frequency (RF) signals directly into digital data for the wireless receiver and, for the transmitter, converts digital data into RF signals. The Software Configurable Multichannel Transceiver (SCMT) enables four transmitters and four receivers in a single unit the size of a commodity disk drive, programmable for any frequency band between 1 MHz and 6 GHz.

  18. Multichannel optical sensing device

    DOEpatents

    Selkowitz, Stephen E.

    1990-01-01

    A multichannel optical sensing device is disclosed, for measuring the outr sky luminance or illuminance or the luminance or illuminance distribution in a room, comprising a plurality of light receptors, an optical shutter matrix including a plurality of liquid crystal optical shutter elements operable by electrical control signals between light transmitting and light stopping conditions, fiber optic elements connected between the receptors and the shutter elements, a microprocessor based programmable control unit for selectively supplying control signals to the optical shutter elements in a programmable sequence, a photodetector including an optical integrating spherical chamber having an input port for receiving the light from the shutter matrix and at least one detector element in the spherical chamber for producing output signals corresponding to the light, and output units for utilizing the output signals including a storage unit having a control connection to the microprocessor based programmable control unit for storing the output signals under the sequence control of the programmable control unit.

  19. Multichannel optical sensing device

    DOEpatents

    Selkowitz, S.E.

    1985-08-16

    A multichannel optical sensing device is disclosed, for measuring the outdoor sky luminance or illuminance or the luminance or illuminance distribution in a room, comprising a plurality of light receptors, an optical shutter matrix including a plurality of liquid crystal optical shutter elements operable by electrical control signals between light transmitting and light stopping conditions, fiber optical elements connected between the receptors and the shutter elements, a microprocessor based programmable control unit for selectively supplying control signals to the optical shutter elements in a programmable sequence, a photodetector including an optical integrating spherical chamber having an input port for receiving the light from the shutter matrix and at least one detector element in the spherical chamber for producing output signals corresponding to the light, and output units for utilizing the output signals including a storage unit having a control connection to the microprocessor based programmable control unit for storing the output signals under the sequence control of the programmable control unit.

  20. HAI: A novel airborne multi-channel hygrometer for fast multi-phase H2O quantification: Performance of the HAI instrument during the first flights on the German HALO aircraft

    NASA Astrophysics Data System (ADS)

    Buchholz, B.; Ebert, V.; Kraemer, M.; Afchine, A.

    2014-12-01

    Common gas phase H2O measurements on fast airborne platforms e.g. using backward facing or "Rosemount"-inlets can lead to a high risk of ice and droplets contamination. In addition, currently no single hygrometer exists that allows a simultaneous, high-speed measurement of all phases (gas, liquid, ice) with the same detection principle. In the rare occasions multi-phase measurements are realized, gas-and condensed-phase observations rely on different methods, instruments and calibration strategies so that precision and accuracy levels are quite difficult to quantify. This is effectively avoided by the novel TDLAS instrument, HAI, Hygrometer for Atmospheric Investigation, which allows a simultaneous, high speed, multi-phase detection without any sensor calibration in a unique "2+2" channel concept. Hai combines two independent wavelength channels, at 1.4 µm and at 2.6 µm, for a wide dynamic range from 1 to 30 000 ppmv, with a simultaneous closed path (extractive) and open path detection. Thus, "Total", i.e. gas-phase plus condensed-phase water is measured by sampling via a forward facing inlet into "closed-path" extractive cells. A selective, sampling-free, high speed gas phase detection is realized via a dual-wavelength "open-path" cell placed outside of the aircraft fuselage. All channels can be sampled with 120 Hz (measurement cycle time Dt=1.6 ms) allowing an unprecedented spatial resolution of 30 cm at 900 km/h. The evaluation of the individual multi-channel raw-data is done post flight, without any channel interdependencies, in calibration-free mode, thus allowing fast, accurate and precise multi-phase water detection in flight. The performance could be shown in more than 200 net flights hours in three scientific flight campaigns (TACTS, ESMVal, ML-CIRRUS) on the new German HALO aircraft. In addition the level of the accuracy of the calibration free evaluation was evaluated at the German national primary water vapor standard.

  1. Multichannel electrochemical microbial detection unit

    NASA Technical Reports Server (NTRS)

    Wilkins, J. R.; Young, R. N.; Boykin, E. H.

    1978-01-01

    The paper describes the design and capabilities of a compact multichannel electrochemical unit devised to detect and automatically indicate detection time length of bacteria. By connecting this unit to a strip-chart recorder, a permanent record is obtained of the end points and growth curves for each of eight channels. The experimental setup utilizing the multichannel unit consists of a test tube (25 by 150 mm) containing a combination redox electrode plus 18 ml of lauryl tryptose broth and positioned in a 35-C water bath. Leads from the electrodes are connected to the multichannel unit, which in turn is connected to a strip-chart recorder. After addition of 2.0 ml of inoculum to the test tubes, depression of the push-button starter activates the electronics, timer, and indicator light for each channel. The multichannel unit is employed to test tenfold dilutions of various members of the Enterobacteriaceae group, and a typical dose-response curve is presented.

  2. Sampled sinusoidal stimulation profile and multichannel fuzzy logic classification for monitor-based phase-coded SSVEP brain-computer interfacing

    NASA Astrophysics Data System (ADS)

    Manyakov, Nikolay V.; Chumerin, Nikolay; Robben, Arne; Combaz, Adrien; van Vliet, Marijn; Van Hulle, Marc M.

    2013-06-01

    Objective. The performance and usability of brain-computer interfaces (BCIs) can be improved by new paradigms, stimulation methods, decoding strategies, sensor technology etc. In this study we introduce new stimulation and decoding methods for electroencephalogram (EEG)-based BCIs that have targets flickering at the same frequency but with different phases. Approach. The phase information is estimated from the EEG data, and used for target command decoding. All visual stimulation is done on a conventional (60-Hz) LCD screen. Instead of the ‘on/off’ visual stimulation, commonly used in phase-coded BCI, we propose one based on a sampled sinusoidal intensity profile. In order to fully exploit the circular nature of the evoked phase response, we introduce a filter feature selection procedure based on circular statistics and propose a fuzzy logic classifier designed to cope with circular information from multiple channels jointly. Main results. We show that the proposed visual stimulation enables us not only to encode more commands under the same conditions, but also to obtain EEG responses with a more stable phase. We also demonstrate that the proposed decoding approach outperforms existing ones, especially for the short time windows used. Significance. The work presented here shows how to overcome some of the limitations of screen-based visual stimulation. The superiority of the proposed decoding approach demonstrates the importance of preserving the circularity of the data during the decoding stage.

  3. Multichannel demultiplexer-demodulator

    NASA Technical Reports Server (NTRS)

    Courtois, Hector; Sherry, Mike; Cangiane, Peter; Caso, Greg

    1993-01-01

    One of the critical satellite technologies in a meshed VSAT (very small aperture terminal) satellite communication networks utilizing FDMA (frequency division multiple access) uplinks is a multichannel demultiplexer/demodulator (MCDD). TRW Electronic Systems Group developed a proof-of-concept (POC) MCDD using advanced digital technologies. This POC model demonstrates the capability of demultiplexing and demodulating multiple low to medium data rate FDMA uplinks with potential for expansion to demultiplexing and demodulating hundreds to thousands of narrowband uplinks. The TRW approach uses baseband sampling followed by successive wideband and narrowband channelizers with each channelizer feeding into a multirate, time-shared demodulator. A full-scale MCDD would consist of an 8 bit A/D sampling at 92.16 MHz, four wideband channelizers capable of demultiplexing eight wideband channels, thirty-two narrowband channelizers capable of demultiplexing one wideband signal into 32 narrowband channels, and thirty-two multirate demodulators. The POC model consists of an 8 bit A/D sampling at 23.04 MHz, one wideband channelizer, 16 narrowband channelizers, and three multirate demodulators. The implementation loss of the wideband and narrowband channels is 0.3dB and 0.75dB at 10(exp -7) E(sub b)/N(sub o) respectively.

  4. Classification of mouth movements using 7 T fMRI

    NASA Astrophysics Data System (ADS)

    Bleichner, M. G.; Jansma, J. M.; Salari, E.; Freudenburg, Z. V.; Raemaekers, M.; Ramsey, N. F.

    2015-12-01

    Objective. A brain-computer interface (BCI) is an interface that uses signals from the brain to control a computer. BCIs will likely become important tools for severely paralyzed patients to restore interaction with the environment. The sensorimotor cortex is a promising target brain region for a BCI due to the detailed topography and minimal functional interference with other important brain processes. Previous studies have shown that attempted movements in paralyzed people generate neural activity that strongly resembles actual movements. Hence decodability for BCI applications can be studied in able-bodied volunteers with actual movements. Approach. In this study we tested whether mouth movements provide adequate signals in the sensorimotor cortex for a BCI. The study was executed using fMRI at 7 T to ensure relevance for BCI with cortical electrodes, as 7 T measurements have been shown to correlate well with electrocortical measurements. Twelve healthy volunteers executed four mouth movements (lip protrusion, tongue movement, teeth clenching, and the production of a larynx activating sound) while in the scanner. Subjects performed a training and a test run. Single trials were classified based on the Pearson correlation values between the activation patterns per trial type in the training run and single trials in the test run in a ‘winner-takes-all’ design. Main results. Single trial mouth movements could be classified with 90% accuracy. The classification was based on an area with a volume of about 0.5 cc, located on the sensorimotor cortex. If voxels were limited to the surface, which is accessible for electrode grids, classification accuracy was still very high (82%). Voxels located on the precentral cortex performed better (87%) than the postcentral cortex (72%). Significance. The high reliability of decoding mouth movements suggests that attempted mouth movements are a promising candidate for BCI in paralyzed people.

  5. A 7T Spine Array Based on Electric Dipole Transmitters

    PubMed Central

    Duan, Qi; Nair, Govind; Gudino, Natalia; de Zwart, Jacco A.; van Gelderen, Peter; Murphy-Boesch, Joe; Reich, Daniel S.; Duyn, Jeff H.; Merkle, Hellmut

    2015-01-01

    Purpose In this work the feasibility of using an array of electric dipole antennas for RF transmission in spine MRI at high field is explored. Method A 2-channel transmit array based on an electric dipole design was quantitatively optimized for 7T spine imaging and integrated with a receive array combining 8 loop coils. Using B1+ mapping, the transmit efficiency of the dipole array was compared to a design using quadrature loop pairs. The radio-frequency (RF) energy deposition for each array was measured using a home-built dielectric phantom and MR thermometry. The performance of the proposed array was qualitatively demonstrated in human studies. Results The results indicate dramatically improved transmit efficiency for the dipole design as compared to the loop excitation. Up to 76% gain was achieved within the spinal region. Conclusion For imaging of the spine, electric-dipole based transmitters provided an attractive alternative to the traditional loop-based design. Easy integration with existing receive array technology facilitates practical use at high field. PMID:26190585

  6. Multichannel homodyne receiver

    DOEpatents

    Landt, Jeremy A.

    1982-01-01

    A homodyne radar transmitter/receiver device which produces a single combined output which contains modulated backscatter information for all phase conditions of both modulated and unmodulated backscatter signals. The device utilizes taps along coaxial transmission lines, strip transmission line, and waveguides which are spaced by 1/8 wavelength or 1/6 wavelength, etc. This greatly reduces costs by eliminating separate transmission and reception antennas and an expensive arrangement of power splitters and mixers utilized in the prior art.

  7. Multichannel homodyne receiver

    DOEpatents

    Landt, J.A.

    1981-01-19

    A homodyne radar transmitter/receiver device which produces a single combined output which contains modulated backscatter information for all phase conditions of both modulated and unmodulated backscatter signals is described. The device utilizes taps along coaxial transmission lines, strip transmission line, and waveguides which are spaced by 1/8 wavelength or 1/6 wavelength, etc. This greatly reduces costs by eliminating separate transmission and reception antennas and an expensive arrangement of power splitters and mixers utilized in the prior art.

  8. Paraplegics standing up using multichannel FES and arm support.

    PubMed

    Kuzelicki, J; Kamnik, R; Bajd, T; Obreza, P; Benko, H

    2002-01-01

    The suitability of multichannel functional electrical stimulation (FES) during the standing-up manoeuvre for therapeutic home use was investigated. Two spinal cord-injured subjects (SCI) participated in the study. Ankle plantar flexors, knee extensors and hip extensors were stimulated. The amplitude of the stimulation pulses depended on the current phase of raising. The sit-to-stand process was divided into three phases by detecting characteristic events in the vertical handle reaction force. It was found that the multichannel FES did not contribute to the decrease of the arm support force when compared with stimulation of knee extensors only. However, stimulation of the hip extensors could speed up the raising process. Increased repeatability and faster standing up were observed when the stimulation began before the start of raising.

  9. Web-based multi-channel analyzer

    DOEpatents

    Gritzo, Russ E.

    2003-12-23

    The present invention provides an improved multi-channel analyzer designed to conveniently gather, process, and distribute spectrographic pulse data. The multi-channel analyzer may operate on a computer system having memory, a processor, and the capability to connect to a network and to receive digitized spectrographic pulses. The multi-channel analyzer may have a software module integrated with a general-purpose operating system that may receive digitized spectrographic pulses for at least 10,000 pulses per second. The multi-channel analyzer may further have a user-level software module that may receive user-specified controls dictating the operation of the multi-channel analyzer, making the multi-channel analyzer customizable by the end-user. The user-level software may further categorize and conveniently distribute spectrographic pulse data employing non-proprietary, standard communication protocols and formats.

  10. PDX multichannel interferometer

    SciTech Connect

    Bitzer, R.; Ernst, W.; Cutsogeorge, G.

    1980-10-01

    A 10 channel, 140 GHz homodyne interferometer is described for use on PDX. One feature of this interferometer is the separation of the signal source and electronics from the power splitters, delay line, and receiving systems. The latter is situated near the upper and lower vacuum ports between the toroidal field magnets. A second feature is the signal stabilization of the EIO source by means of an AFC system. The complete interferometer is described including block diagrams, circuit diagrams, test data, and magnetic field test conducted on the preamplifiers, microwave diodes, isolators, etc., to determine the extent of magnetic shielding required. The description of the tracking filters and digital phase display circuit is referenced to accompanying reports.

  11. [Research progress of techniques of 7 T MRI system in brain imaging].

    PubMed

    Lin, Lan; Hao, Dongmei; Bai, Yanping; Gao, Hongjian; Wu, Shuicai

    2013-10-01

    7 T high field magnetic resonance imaging (MRI) provides a useful tool for microscopic spatial resolution visualizing anatomy. In addition, it enables the observation and analysis of tissue metabolism and function. 7 T MRI is now developing fast both in its technology and in its potential prospective medical applications. This review introduces current applications and possible future developments of the 7 T MRI in the field of human brain imaging for clinical studies and practices.

  12. Reconstruction of 7T-Like Images From 3T MRI.

    PubMed

    Bahrami, Khosro; Shi, Feng; Zong, Xiaopeng; Shin, Hae Won; An, Hongyu; Shen, Dinggang

    2016-09-01

    In the recent MRI scanning, ultra-high-field (7T) MR imaging provides higher resolution and better tissue contrast compared to routine 3T MRI, which may help in more accurate and early brain diseases diagnosis. However, currently, 7T MRI scanners are more expensive and less available at clinical and research centers. These motivate us to propose a method for the reconstruction of images close to the quality of 7T MRI, called 7T-like images, from 3T MRI, to improve the quality in terms of resolution and contrast. By doing so, the post-processing tasks, such as tissue segmentation, can be done more accurately and brain tissues details can be seen with higher resolution and contrast. To do this, we have acquired a unique dataset which includes paired 3T and 7T images scanned from same subjects, and then propose a hierarchical reconstruction based on group sparsity in a novel multi-level Canonical Correlation Analysis (CCA) space, to improve the quality of 3T MR image to be 7T-like MRI. First, overlapping patches are extracted from the input 3T MR image. Then, by extracting the most similar patches from all the aligned 3T and 7T images in the training set, the paired 3T and 7T dictionaries are constructed for each patch. It is worth noting that, for the training, we use pairs of 3T and 7T MR images from each training subject. Then, we propose multi-level CCA to map the paired 3T and 7T patch sets to a common space to increase their correlations. In such space, each input 3T MRI patch is sparsely represented by the 3T dictionary and then the obtained sparse coefficients are used together with the corresponding 7T dictionary to reconstruct the 7T-like patch. Also, to have the structural consistency between adjacent patches, the group sparsity is employed. This reconstruction is performed with changing patch sizes in a hierarchical framework. Experiments have been done using 13 subjects with both 3T and 7T MR images. The results show that our method outperforms previous

  13. Reconstruction of 7T-Like Images From 3T MRI.

    PubMed

    Bahrami, Khosro; Shi, Feng; Zong, Xiaopeng; Shin, Hae Won; An, Hongyu; Shen, Dinggang

    2016-09-01

    In the recent MRI scanning, ultra-high-field (7T) MR imaging provides higher resolution and better tissue contrast compared to routine 3T MRI, which may help in more accurate and early brain diseases diagnosis. However, currently, 7T MRI scanners are more expensive and less available at clinical and research centers. These motivate us to propose a method for the reconstruction of images close to the quality of 7T MRI, called 7T-like images, from 3T MRI, to improve the quality in terms of resolution and contrast. By doing so, the post-processing tasks, such as tissue segmentation, can be done more accurately and brain tissues details can be seen with higher resolution and contrast. To do this, we have acquired a unique dataset which includes paired 3T and 7T images scanned from same subjects, and then propose a hierarchical reconstruction based on group sparsity in a novel multi-level Canonical Correlation Analysis (CCA) space, to improve the quality of 3T MR image to be 7T-like MRI. First, overlapping patches are extracted from the input 3T MR image. Then, by extracting the most similar patches from all the aligned 3T and 7T images in the training set, the paired 3T and 7T dictionaries are constructed for each patch. It is worth noting that, for the training, we use pairs of 3T and 7T MR images from each training subject. Then, we propose multi-level CCA to map the paired 3T and 7T patch sets to a common space to increase their correlations. In such space, each input 3T MRI patch is sparsely represented by the 3T dictionary and then the obtained sparse coefficients are used together with the corresponding 7T dictionary to reconstruct the 7T-like patch. Also, to have the structural consistency between adjacent patches, the group sparsity is employed. This reconstruction is performed with changing patch sizes in a hierarchical framework. Experiments have been done using 13 subjects with both 3T and 7T MR images. The results show that our method outperforms previous

  14. Simultaneous gas-phase and total water detection for airborne applications with a multi-channel TDL spectrometer at 1.4 μm and 2.6 μm

    NASA Astrophysics Data System (ADS)

    Buchholz, Bernhard; Afchine, Armin; Klein, Alexander; Barthel, Jochen; Kallweit, Sören; Klostermann, Tim; Krämer, Martina; Schiller, Cornelius; Ebert, Volker

    2013-04-01

    Water vapor measurements especially within clouds are difficult, in particular due to numerous instrument-specific limitations in precision, time resolution and accuracy. Notably the quantification of the ice and gas-phase water content in cirrus clouds, which play an important role in the global climate system, require new high-speed hygrometers concepts which are capable of resolving large water vapor gradients. Previously we demonstrated a stationary concept of a Tunable Diode Laser Absorption Spectroscopy (TDLAS)-based quantification of the ice/liquid water by independent, but simultaneous measurements of A) the gas-phase water in an open-path configuration (optical-path 125 m) and B) the total water in an extractive version with a closed cell (30 m path) after evaporating the condensed water [1]. In this case we used laboratory TDLAS instrumentation in combination with a long absorption paths and applied those to the AIDA cloud camber [2]. Recently we developed an advanced, miniature version of the concept, suitable for mobile field applications and in particular for use on aircrafts. First tests of our new, fiber-coupled open-path TDLAS cell [3] for airborne applications were combined with the experiences of our extractive SEALDH instruments [4] and led to a new, multi-channel, "multi-phase TDL-hygrometer" called "HAI" ("Hygrometer for Atmospheric Investigations"). HAI, which is explicitly designed for the new German HALO (High Altitude and Long Range Research Aircraft) airplane, provides a similar, but improved functionality like the stationary, multi-phase TDLAS developed for AIDA. However HAI comes in a much more compact, six height units, 30 kg, electronics rack for the main unit and with a new, completely fiber-coupled, compact, 21 kg, dual-wavelength open-path TDL-cell which is placed in the aircraft's skin. HAI is much more complex and versatile than the AIDA precursor and can be seen as comprised of four TDL-spectrometers, as it simultaneously

  15. A Student-Made Inexpensive Multichannel Pipet

    ERIC Educational Resources Information Center

    Dragojlovic, Veljko

    2009-01-01

    An inexpensive multichannel pipet designed to deliver small volumes of liquid simultaneously to wells in a multiwell plate can be prepared by students in a single laboratory period. The multichannel pipet is made of disposable plastic 1 mL syringes and drilled plastic plates, which are used to make plunger and barrel assemblies. Application of the…

  16. Multichannel decision feedback equalization in underwater acoustic communication

    NASA Astrophysics Data System (ADS)

    Yang, Xiaoxia; Wang, Haibin; Wang, Jun

    2012-11-01

    This paper studies an underwater acoustic communication system and its performance in shallow water. A channel encoder and a quadrature phase shift keying (QPSK) modulation scheme have been adopted at the transmitter, and a multichannel decision feedback equalizer (DFE) with a soft decision device has been used at the receiver. This system has been tested in a Yellow Sea experiment for transmitting an image at a range of 18.5km. A space diversity procedure is used to mitigate the performance degradation of the multichannel DFE caused by occasional impulsive noise in the receiver. In the case of two receivers, the equalizer exhibits good performance with bit error number of 319 out of 239946. After channel decoding, an image is obtained without any errant bits.

  17. Least squares restoration of multichannel images

    NASA Technical Reports Server (NTRS)

    Galatsanos, Nikolas P.; Katsaggelos, Aggelos K.; Chin, Roland T.; Hillery, Allen D.

    1991-01-01

    Multichannel restoration using both within- and between-channel deterministic information is considered. A multichannel image is a set of image planes that exhibit cross-plane similarity. Existing optimal restoration filters for single-plane images yield suboptimal results when applied to multichannel images, since between-channel information is not utilized. Multichannel least squares restoration filters are developed using the set theoretic and the constrained optimization approaches. A geometric interpretation of the estimates of both filters is given. Color images (three-channel imagery with red, green, and blue components) are considered. Constraints that capture the within- and between-channel properties of color images are developed. Issues associated with the computation of the two estimates are addressed. A spatially adaptive, multichannel least squares filter that utilizes local within- and between-channel image properties is proposed. Experiments using color images are described.

  18. Virtual Microphones for Multichannel Audio Resynthesis

    NASA Astrophysics Data System (ADS)

    Mouchtaris, Athanasios; Narayanan, Shrikanth S.; Kyriakakis, Chris

    2003-12-01

    Multichannel audio offers significant advantages for music reproduction, including the ability to provide better localization and envelopment, as well as reduced imaging distortion. On the other hand, multichannel audio is a demanding media type in terms of transmission requirements. Often, bandwidth limitations prohibit transmission of multiple audio channels. In such cases, an alternative is to transmit only one or two reference channels and recreate the rest of the channels at the receiving end. Here, we propose a system capable of synthesizing the required signals from a smaller set of signals recorded in a particular venue. These synthesized "virtual" microphone signals can be used to produce multichannel recordings that accurately capture the acoustics of that venue. Applications of the proposed system include transmission of multichannel audio over the current Internet infrastructure and, as an extension of the methods proposed here, remastering existing monophonic and stereophonic recordings for multichannel rendering.

  19. Quantitative prediction of radio frequency induced local heating derived from measured magnetic field maps in magnetic resonance imaging: A phantom validation at 7 T

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaotong; Van de Moortele, Pierre-Francois; Liu, Jiaen; Schmitter, Sebastian; He, Bin

    2014-12-01

    Electrical Properties Tomography (EPT) technique utilizes measurable radio frequency (RF) coil induced magnetic fields (B1 fields) in a Magnetic Resonance Imaging (MRI) system to quantitatively reconstruct the local electrical properties (EP) of biological tissues. Information derived from the same data set, e.g., complex numbers of B1 distribution towards electric field calculation, can be used to estimate, on a subject-specific basis, local Specific Absorption Rate (SAR). SAR plays a significant role in RF pulse design for high-field MRI applications, where maximum local tissue heating remains one of the most constraining limits. The purpose of the present work is to investigate the feasibility of such B1-based local SAR estimation, expanding on previously proposed EPT approaches. To this end, B1 calibration was obtained in a gelatin phantom at 7 T with a multi-channel transmit coil, under a particular multi-channel B1-shim setting (B1-shim I). Using this unique set of B1 calibration, local SAR distribution was subsequently predicted for B1-shim I, as well as for another B1-shim setting (B1-shim II), considering a specific set of parameter for a heating MRI protocol consisting of RF pulses plaid at 1% duty cycle. Local SAR results, which could not be directly measured with MRI, were subsequently converted into temperature change which in turn were validated against temperature changes measured by MRI Thermometry based on the proton chemical shift.

  20. Multichannel laser-fiber vibrometer

    NASA Astrophysics Data System (ADS)

    Dudzik, Grzegorz; Waz, Adam; Kaczmarek, Pawel; Antonczak, Arkadiusz; Sotor, Jaroslaw; Krzempek, Karol; Sobon, Grzegorz; Abramski, Krzysztof M.

    2013-01-01

    For the last few years we were elaborating the laser-fiber vibrometer working at 1550 nm. Our main stress was directed towards different aspects of research: analysis of scattered light, efficient photodetection, optimization of the fiber-free space interfaces and signal processing. As a consequence we proposed the idea of a multichannel fiber vibrometer based on well developed telecommunication technique - Wavelength Division Multiplexing (WDM). One of the most important parts of a fiber-laser vibrometer is demodulation electronic section. The distortion, nonlinearity, offset and added noise of measured signal come from electronic circuits and they have direct influence on finale measuring results. We present the results of finished project "Developing novel laser-fiber monitoring technologies to prevent environmental hazards from vibrating objects" where we have constructed a 4-channel WDM laser-fiber vibrometer.

  1. Multichannel Spectrometer of Time Distribution

    NASA Astrophysics Data System (ADS)

    Akindinova, E. V.; Babenko, A. G.; Vakhtel, V. M.; Evseev, N. A.; Rabotkin, V. A.; Kharitonova, D. D.

    2015-06-01

    For research and control of characteristics of radiation fluxes, radioactive sources in particular, for example, in paper [1], a spectrometer and methods of data measurement and processing based on the multichannel counter of time intervals of accident events appearance (impulses of particle detector) MC-2A (SPC "ASPECT") were created. The spectrometer has four independent channels of registration of time intervals of impulses appearance and correspondent amplitude and spectrometric channels for control along the energy spectra of the operation stationarity of paths of each of the channels from the detector to the amplifier. The registration of alpha-radiation is carried out by the semiconductor detectors with energy resolution of 16-30 keV. Using a spectrometer there have been taken measurements of oscillations of alpha-radiation 239-Pu flux intensity with a subsequent autocorrelative statistical analysis of the time series of readings.

  2. Multi-channel polarized thermal emitter

    DOEpatents

    Lee, Jae-Hwang; Ho, Kai-Ming; Constant, Kristen P

    2013-07-16

    A multi-channel polarized thermal emitter (PTE) is presented. The multi-channel PTE can emit polarized thermal radiation without using a polarizer at normal emergence. The multi-channel PTE consists of two layers of metallic gratings on a monolithic and homogeneous metallic plate. It can be fabricated by a low-cost soft lithography technique called two-polymer microtransfer molding. The spectral positions of the mid-infrared (MIR) radiation peaks can be tuned by changing the periodicity of the gratings and the spectral separation between peaks are tuned by changing the mutual angle between the orientations of the two gratings.

  3. A Multichannel Bioluminescence Determination Platform for Bioassays.

    PubMed

    Kim, Sung-Bae; Naganawa, Ryuichi

    2016-01-01

    The present protocol introduces a multichannel bioluminescence determination platform allowing a high sample throughput determination of weak bioluminescence with reduced standard deviations. The platform is designed to carry a multichannel conveyer, an optical filter, and a mirror cap. The platform enables us to near-simultaneously determine ligands in multiple samples without the replacement of the sample tubes. Furthermore, the optical filters beneath the multichannel conveyer are designed to easily discriminate colors during assays. This optical system provides excellent time- and labor-efficiency to users during bioassays. PMID:27424912

  4. A Multichannel Bioluminescence Determination Platform for Bioassays.

    PubMed

    Kim, Sung-Bae; Naganawa, Ryuichi

    2016-01-01

    The present protocol introduces a multichannel bioluminescence determination platform allowing a high sample throughput determination of weak bioluminescence with reduced standard deviations. The platform is designed to carry a multichannel conveyer, an optical filter, and a mirror cap. The platform enables us to near-simultaneously determine ligands in multiple samples without the replacement of the sample tubes. Furthermore, the optical filters beneath the multichannel conveyer are designed to easily discriminate colors during assays. This optical system provides excellent time- and labor-efficiency to users during bioassays.

  5. Classification of the venous architecture of the pineal gland by 7T MRI.

    PubMed

    Cho, Zang-Hee; Choi, Sang-Han; Chi, Je-Gun; Kim, Young-Bo

    2011-10-01

    Magnetic resonance imaging (MRI) at 7.0 Tesla (7T) can show many details of anatomical structures with unprecedented resolution and contrast. In this report, we describe for the first time the unexpected wide variation in pineal gland structure, as visualized by MR images obtained with 7T in a group of healthy young volunteers. A total of 34 volunteers (22 men and 12 women) were enrolled in the study. Their 7T MR images revealed such wide variations in pineal gland shape that it led us to attempt to classify the patterns seen in these pineal glands. Indeed, they were successfully correlated with a previous human cadaver study of venous structures by Tamaki et al., who classified the venous structures of the pineal gland into three categories. This is the first human in vivo pineal vein imaging study using 7T MRI. Pineal venous imaging may permit the early diagnosis of a pineal tumor.

  6. A subfemtotesla multichannel atomic magnetometer.

    PubMed

    Kominis, I K; Kornack, T W; Allred, J C; Romalis, M V

    2003-04-10

    The magnetic field is one of the most fundamental and ubiquitous physical observables, carrying information about all electromagnetic phenomena. For the past 30 years, superconducting quantum interference devices (SQUIDs) operating at 4 K have been unchallenged as ultrahigh-sensitivity magnetic field detectors, with a sensitivity reaching down to 1 fT Hz(-1/2) (1 fT = 10(-15) T). They have enabled, for example, mapping of the magnetic fields produced by the brain, and localization of the underlying electrical activity (magnetoencephalography). Atomic magnetometers, based on detection of Larmor spin precession of optically pumped atoms, have approached similar levels of sensitivity using large measurement volumes, but have much lower sensitivity in the more compact designs required for magnetic imaging applications. Higher sensitivity and spatial resolution combined with non-cryogenic operation of atomic magnetometers would enable new applications, including the possibility of mapping non-invasively the cortical modules in the brain. Here we describe a new spin-exchange relaxation-free (SERF) atomic magnetometer, and demonstrate magnetic field sensitivity of 0.54 fT Hz(-1/2) with a measurement volume of only 0.3 cm3. Theoretical analysis shows that fundamental sensitivity limits of this device are below 0.01 fT Hz(-1/2). We also demonstrate simple multichannel operation of the magnetometer, and localization of magnetic field sources with a resolution of 2 mm.

  7. Comparing neural response to painful electrical stimulation with functional MRI at 3 and 7 T.

    PubMed

    Hahn, Andreas; Kranz, Georg S; Seidel, Eva-Maria; Sladky, Ronald; Kraus, Christoph; Küblböck, Martin; Pfabigan, Daniela M; Hummer, Allan; Grahl, Arvina; Ganger, Sebastian; Windischberger, Christian; Lamm, Claus; Lanzenberger, Rupert

    2013-11-15

    Progressing from 3T to 7 T functional MRI enables marked improvements of human brain imaging in vivo. Although direct comparisons demonstrated advantages concerning blood oxygen level dependent (BOLD) signal response and spatial specificity, these mostly focused on single brain regions with rather simple tasks. Considering that physiological noise also increases with higher field strength, it is not entirely clear whether the advantages of 7T translate equally to the entire brain during tasks which elicit more complex neuronal processing. Therefore, we investigated the difference between 3T and 7 T in response to transcutaneous electrical painful and non-painful stimulation in 22 healthy subjects. For painful stimuli vs. baseline, stronger activations were observed at 7 T in several brain regions including the insula and supplementary motor area, but not the secondary somatosensory cortex (p<0.05 FWE-corrected). Contrasting painful vs. non-painful stimulation limited the differences between the field strengths to the periaqueductal gray (PAG, p<0.001 uncorrected) due to a similar signal increase at 7 T for both the target and specific control condition in most brain regions. This regional specificity obtained for the PAG at higher field strengths was confirmed by an additional spatial normalization strategy optimized for the brainstem. Here, robust BOLD responses were obtained in the dorsal PAG at 7 T (p<0.05 FWE-corrected), whereas at 3T activation was completely missing for the contrast against non-painful stimuli. To summarize, our findings support previously reported benefits obtained at ultra-high field strengths also for complex activation patterns elicited by painful electrical stimulation. However, this advantage depends on the region and even more on the contrast of interest. The greatest gain at 7 T was observed within the small brainstem region of the PAG, where the increased field strength offered marked improvement for the localization of activation

  8. [A method for improving measuring accuracy in multi-channel impedance spectroscopy (MIS)].

    PubMed

    Thiel, F; Hartung, C

    2004-08-01

    The use of impedance spectroscopy as a diagnostic tool for the investigation of biological objects involves the consideration of numerous parameters impacting on measuring accuracy. This paper describes a calibration method for multichannel instruments that reduces the non-inconsiderable influence of frequency response variations between the channels, thus significantly increasing measuring accuracy. The method is tested in a recently developed, high-resolution, multi-channel bio-impedance analyser. Reduction of the measuring error is demonstrated, and the magnitude and phase resolution is quantified. The advantage of this method lies in its applicability to existing systems. Furthermore, an additional calibration impedance is not needed. PMID:15481406

  9. Design and Simulation of a Birdcage Coil using CST Studio Suite for Application at 7T

    NASA Astrophysics Data System (ADS)

    Palau Tomas, Bernat; Li, Houmin; Anjum, M. R.

    2013-12-01

    This work describes the study of coils for Magnetic Resonance Imaging (MRI) applications. The principal objective is the design of a birdcage Radio Frequency (RF) coil to use in a 7 Tesla (7T) scanner. Higher strength field generates a better SNR and increased chemical shift effect, improving spectral fat suppression and spectroscopy. Moreover, a better SNR increases the spatial resolution or reduces the imaging time. This research work presented recent developments based on high field 7T design using CST studio. The birdcage coil achieves circular polarization and generates a high homogeneous radio frequency magnetic field under many conditions. Design of a Birdcage coil for a 7T to obtain the images from s mall animals (i.e. mouse). It opens the door to design and construct a Birdcage coil for a 7T to obtain human brain images. Firstly we design a birdcage coil then the results are obtained with simulator CST Wave Studio, creating a 3D model and generating a simulation. Finally the parameters are re adjusted to obtain our desired Larmor frequency 298.2 MHz for a correct operation in 7T. This research work demonstrates the theoretical results from our design and shows the designed antenna behavior.

  10. Multichannel photocells for image converters with color separation

    SciTech Connect

    Denisova, E. A.; Uzdovskii, V. V. Khainovskii, V. I.

    2011-12-15

    The results of a study of photoelectric processes in photosensitive structures based on a multichannel vertically integrated p-n junction are presented. Optical radiation absorption in the space-charge region of a multichannel vertically integrated structure is studied.

  11. Restoration of multichannel microwave radiometric images

    NASA Technical Reports Server (NTRS)

    Chin, R. T.; Yeh, C.-L.; Olson, W. S.

    1985-01-01

    A constrained iterative image restoration method is applied to multichannel diffraction-limited imagery. This method is based on the Gerchberg-Papoulis algorithm utilizing incomplete information and partial constraints. The procedure is described using the orthogonal projection operators which project onto two prescribed subspaces iteratively. Its properties and limitations are presented. The effect of noise was investigated and a better understanding of the performance of the algorithm with noisy data has been achieved. The restoration scheme with the selection of appropriate constraints was applied to a practical problem. The 6.6, 10.7, 18, and 21 GHz satellite images obtained by the scanning multichannel microwave radiometer (SMMR), each having different spatial resolution, were restored to a common, high resolution (that of the 37 GHz channels) to demonstrate the effectiveness of the method. Both simulated data and real data were used in this study. The restored multichannel images may be utilized to retrieve rainfall distributions.

  12. Multichannel framework for singular quantum mechanics

    SciTech Connect

    Camblong, Horacio E.; Epele, Luis N.; Fanchiotti, Huner; García Canal, Carlos A.; Ordóñez, Carlos R.

    2014-01-15

    A multichannel S-matrix framework for singular quantum mechanics (SQM) subsumes the renormalization and self-adjoint extension methods and resolves its boundary-condition ambiguities. In addition to the standard channel accessible to a distant (“asymptotic”) observer, one supplementary channel opens up at each coordinate singularity, where local outgoing and ingoing singularity waves coexist. The channels are linked by a fully unitary S-matrix, which governs all possible scenarios, including cases with an apparent nonunitary behavior as viewed from asymptotic distances. -- Highlights: •A multichannel framework is proposed for singular quantum mechanics and analogues. •The framework unifies several established approaches for singular potentials. •Singular points are treated as new scattering channels. •Nonunitary asymptotic behavior is subsumed in a unitary multichannel S-matrix. •Conformal quantum mechanics and the inverse quartic potential are highlighted.

  13. Restoration of multichannel microwave radiometric images

    NASA Technical Reports Server (NTRS)

    Chin, R. T.; Yeh, C. L.; Olson, W. S.

    1983-01-01

    A constrained iterative image restoration method is applied to multichannel diffraction-limited imagery. This method is based on the Gerchberg-Papoulis algorithm utilizing incomplete information and partial constraints. The procedure is described using the orthogonal projection operators which project onto two prescribed subspaces iteratively. Some of its properties and limitations are also presented. The selection of appropriate constraints was emphasized in a practical application. Multichannel microwave images, each having different spatial resolution, were restored to a common highest resolution to demonstrate the effectiveness of the method. Both noise-free and noisy images were used in this investigation.

  14. Optical multichannel sensing of skin blood pulsations

    NASA Astrophysics Data System (ADS)

    Spigulis, Janis; Erts, Renars; Kukulis, Indulis; Ozols, Maris; Prieditis, Karlis

    2004-09-01

    Time resolved detection and analysis of the skin back-scattered optical signals (reflection photoplethysmography or PPG) provide information on skin blood volume pulsations and can serve for cardiovascular assessment. The multi-channel PPG concept has been developed and clinically verified in this study. Portable two- and four-channel PPG monitoring devices have been designed for real-time data acquisition and processing. The multi-channel devices were successfully applied for cardiovascular fitness tests and for early detection of arterial occlusions in extremities. The optically measured heartbeat pulse wave propagation made possible to estimate relative arterial resistances for numerous patients and healthy volunteers.

  15. 26 CFR 1.892-7T - Relationship to other Internal Revenue Code sections (temporary regulations).

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 26 Internal Revenue 9 2010-04-01 2010-04-01 false Relationship to other Internal Revenue Code...-7T Relationship to other Internal Revenue Code sections (temporary regulations). (a) Section 893. The... foreign central bank of issue (as defined in § 1.895-1(b)) that fails to qualify for the exemption...

  16. Proton magnetic resonance spectroscopy in deep human brain structures at 7 T

    NASA Astrophysics Data System (ADS)

    Elywa, M.; Mulla-Osman, S.; Godenschweger, F.; Speck, O.

    2012-03-01

    The increased magnetization and frequency separation at high magnetic field strength, such as 7 T, can provide spectra of high signal-to-noise ratio and spectral resolution. However, most human brain magnetic resonance spectroscopy (MRS) studies at 7 T have employed surface coils and thus limited to superficial brain structures. In this study, volume coil excitation together with volume array reception has been utilized to access deeper brain areas. RF power limitations have been addressed by the use of VERSE-modified pulses, and spectra in parietal and pregenual anterior cingulate cortex (pgACC) have been acquired in eight subjects using STEAM with a short echo time of 20 ms. Spectra were analyzed using LC-model. Therefore, an experimental basis set of in vitro spectra was established from 20 human brain metabolite solutions. An exemplary comparison with an optimized PRESS-based single voxel MRS method at 3 T has been performed. Despite the intrinsically lower signal in STEAM, the 7 T spectra show 1.87 times higher signal-to-noise ratio than at 3 T (using PRESS) and more metabolites could be quantified reliably. The results show that the proposed method can be employed at 7 T in deep brain structures and allows the absolute and relative concentrations of human brain metabolites to be determined with low error levels.

  17. 26 CFR 1.1275-7T - Inflation-indexed debt instruments (temporary).

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 26 Internal Revenue 11 2012-04-01 2012-04-01 false Inflation-indexed debt instruments (temporary... Losses § 1.1275-7T Inflation-indexed debt instruments (temporary). (a) through (h) For further guidance, see § 1.1275-7(a) through (h). (i) (j) Treasury Inflation-Protected Securities issued with more than...

  18. Multichannel analyzers at high rates of input

    NASA Technical Reports Server (NTRS)

    Rudnick, S. J.; Strauss, M. G.

    1969-01-01

    Multichannel analyzer, used with a gating system incorporating pole-zero compensation, pile-up rejection, and baseline-restoration, achieves good resolution at high rates of input. It improves resolution, reduces tailing and rate-contributed continuum, and eliminates spectral shift.

  19. Multi-channel electric aerosol spectrometer

    NASA Astrophysics Data System (ADS)

    Mirme, A.; Noppel, M.; Peil, I.; Salm, J.; Tamm, E.; Tammet, H.

    Multi-channel electric mobility spectrometry is a most efficient technique for the rapid measurement of an unstable aerosol particle size spectrum. The measuring range of the spectrometer from 10 microns to 10 microns is achieved by applying diffusional and field charging mechanisms simultaneously. On-line data processing is carried out with a microcomputer. Experimental calibration ensures correctness of measurement.

  20. A multi-channel waveform digitizer system

    SciTech Connect

    Bieser, F.; Muller, W.F.J. )

    1990-04-01

    The authors report on the design and performance of a multichannel waveform digitizer system for use with the Multiple Sample Ionization Chamber (MUSIC) Detector at the Bevalac. 128 channels of 20 MHz Flash ADC plus 256 word deep memory are housed in a single crate. Digital thresholds and hit pattern logic facilitate zero suppression during readout which is performed over a standard VME bus.

  1. Multichannel compressive sensing MRI using noiselet encoding.

    PubMed

    Pawar, Kamlesh; Egan, Gary; Zhang, Jingxin

    2015-01-01

    The incoherence between measurement and sparsifying transform matrices and the restricted isometry property (RIP) of measurement matrix are two of the key factors in determining the performance of compressive sensing (CS). In CS-MRI, the randomly under-sampled Fourier matrix is used as the measurement matrix and the wavelet transform is usually used as sparsifying transform matrix. However, the incoherence between the randomly under-sampled Fourier matrix and the wavelet matrix is not optimal, which can deteriorate the performance of CS-MRI. Using the mathematical result that noiselets are maximally incoherent with wavelets, this paper introduces the noiselet unitary bases as the measurement matrix to improve the incoherence and RIP in CS-MRI. Based on an empirical RIP analysis that compares the multichannel noiselet and multichannel Fourier measurement matrices in CS-MRI, we propose a multichannel compressive sensing (MCS) framework to take the advantage of multichannel data acquisition used in MRI scanners. Simulations are presented in the MCS framework to compare the performance of noiselet encoding reconstructions and Fourier encoding reconstructions at different acceleration factors. The comparisons indicate that multichannel noiselet measurement matrix has better RIP than that of its Fourier counterpart, and that noiselet encoded MCS-MRI outperforms Fourier encoded MCS-MRI in preserving image resolution and can achieve higher acceleration factors. To demonstrate the feasibility of the proposed noiselet encoding scheme, a pulse sequences with tailored spatially selective RF excitation pulses was designed and implemented on a 3T scanner to acquire the data in the noiselet domain from a phantom and a human brain. The results indicate that noislet encoding preserves image resolution better than Fouirer encoding. PMID:25965548

  2. Multichannel compressive sensing MRI using noiselet encoding.

    PubMed

    Pawar, Kamlesh; Egan, Gary; Zhang, Jingxin

    2015-01-01

    The incoherence between measurement and sparsifying transform matrices and the restricted isometry property (RIP) of measurement matrix are two of the key factors in determining the performance of compressive sensing (CS). In CS-MRI, the randomly under-sampled Fourier matrix is used as the measurement matrix and the wavelet transform is usually used as sparsifying transform matrix. However, the incoherence between the randomly under-sampled Fourier matrix and the wavelet matrix is not optimal, which can deteriorate the performance of CS-MRI. Using the mathematical result that noiselets are maximally incoherent with wavelets, this paper introduces the noiselet unitary bases as the measurement matrix to improve the incoherence and RIP in CS-MRI. Based on an empirical RIP analysis that compares the multichannel noiselet and multichannel Fourier measurement matrices in CS-MRI, we propose a multichannel compressive sensing (MCS) framework to take the advantage of multichannel data acquisition used in MRI scanners. Simulations are presented in the MCS framework to compare the performance of noiselet encoding reconstructions and Fourier encoding reconstructions at different acceleration factors. The comparisons indicate that multichannel noiselet measurement matrix has better RIP than that of its Fourier counterpart, and that noiselet encoded MCS-MRI outperforms Fourier encoded MCS-MRI in preserving image resolution and can achieve higher acceleration factors. To demonstrate the feasibility of the proposed noiselet encoding scheme, a pulse sequences with tailored spatially selective RF excitation pulses was designed and implemented on a 3T scanner to acquire the data in the noiselet domain from a phantom and a human brain. The results indicate that noislet encoding preserves image resolution better than Fouirer encoding.

  3. Multichannel Compressive Sensing MRI Using Noiselet Encoding

    PubMed Central

    Pawar, Kamlesh; Egan, Gary; Zhang, Jingxin

    2015-01-01

    The incoherence between measurement and sparsifying transform matrices and the restricted isometry property (RIP) of measurement matrix are two of the key factors in determining the performance of compressive sensing (CS). In CS-MRI, the randomly under-sampled Fourier matrix is used as the measurement matrix and the wavelet transform is usually used as sparsifying transform matrix. However, the incoherence between the randomly under-sampled Fourier matrix and the wavelet matrix is not optimal, which can deteriorate the performance of CS-MRI. Using the mathematical result that noiselets are maximally incoherent with wavelets, this paper introduces the noiselet unitary bases as the measurement matrix to improve the incoherence and RIP in CS-MRI. Based on an empirical RIP analysis that compares the multichannel noiselet and multichannel Fourier measurement matrices in CS-MRI, we propose a multichannel compressive sensing (MCS) framework to take the advantage of multichannel data acquisition used in MRI scanners. Simulations are presented in the MCS framework to compare the performance of noiselet encoding reconstructions and Fourier encoding reconstructions at different acceleration factors. The comparisons indicate that multichannel noiselet measurement matrix has better RIP than that of its Fourier counterpart, and that noiselet encoded MCS-MRI outperforms Fourier encoded MCS-MRI in preserving image resolution and can achieve higher acceleration factors. To demonstrate the feasibility of the proposed noiselet encoding scheme, a pulse sequences with tailored spatially selective RF excitation pulses was designed and implemented on a 3T scanner to acquire the data in the noiselet domain from a phantom and a human brain. The results indicate that noislet encoding preserves image resolution better than Fouirer encoding. PMID:25965548

  4. Compressed sensing sodium MRI of cartilage at 7T: Preliminary study

    NASA Astrophysics Data System (ADS)

    Madelin, Guillaume; Chang, Gregory; Otazo, Ricardo; Jerschow, Alexej; Regatte, Ravinder R.

    2012-01-01

    Sodium MRI has been shown to be highly specific for glycosaminoglycan (GAG) content in articular cartilage, the loss of which is an early sign of osteoarthritis (OA). Quantitative sodium MRI techniques are therefore under development in order to detect and assess early biochemical degradation of cartilage, but due to low sodium NMR sensitivity and its low concentration, sodium images need long acquisition times (15-25 min) even at high magnetic fields and are typically of low resolution. In this preliminary study, we show that compressed sensing can be applied to reduce the acquisition time by a factor of 2 at 7T without losing sodium quantification accuracy. Alternatively, the nonlinear reconstruction technique can be used to denoise fully-sampled images. We expect to even further reduce this acquisition time by using parallel imaging techniques combined with SNR-improved 3D sequences at 3T and 7T.

  5. Compressed Sensing Sodium MRI of Cartilage at 7T: Preliminary Study

    PubMed Central

    Madelin, Guillaume; Chang, Gregory; Otazo, Ricardo; Jerschow, Alexej; Regatte, Ravinder R.

    2012-01-01

    Sodium MRI has been shown to be highly specific for glycosaminoglycan (GAG) content in articular cartilage, the loss of which is an early sign of osteoarthritis (OA). Quantitative sodium MRI techniques are therefore under development in order to detect and assess early biochemical degradation of cartilage, but due to low sodium NMR sensitivity and its low concentration, sodium images need long acquisition times (15 to 25 min) even at high magnetic fields and are typically of low resolution. In this preliminary study, we show that compressed sensing can be applied to reduce the acquisition time by a factor of 2 at 7T without losing sodium quantification accuracy. Alternatively, the nonlinear reconstruction technique can be used to denoise fully-sampled images. We expect to even further reduce this acquisition time by using parallel imaging techniques combined with SNR-improved 3D sequences at 3T and 7T. PMID:22204825

  6. The Neuromelanin-related T2* Contrast in Postmortem Human Substantia Nigra with 7T MRI

    PubMed Central

    Lee, Jae-Hyeok; Baek, Sun-Yong; Song, YoungKyu; Lim, Sujeong; Lee, Hansol; Nguyen, Minh Phuong; Kim, Eun-Joo; Huh, Gi Yeong; Chun, Se Young; Cho, HyungJoon

    2016-01-01

    High field magnetic resonance imaging (MRI)-based delineation of the substantia nigra (SN) and visualization of its inner cellular organization are promising methods for the evaluation of morphological changes associated with neurodegenerative diseases; however, corresponding MR contrasts must be matched and validated with quantitative histological information. Slices from two postmortem SN samples were imaged with a 7 Tesla (7T) MRI with T1 and T2* imaging protocols and then stained with Perl’s Prussian blue, Kluver-Barrera, tyrosine hydroxylase, and calbindin immunohistochemistry in a serial manner. The association between T2* values and quantitative histology was investigated with a co-registration method that accounts for histology slice preparation. The ventral T2* hypointense layers between the SNr and the crus cerebri extended anteriorly to the posterior part of the crus cerebri, which demonstrates the difficulty with an MRI-based delineation of the SN. We found that the paramagnetic hypointense areas within the dorsolateral SN corresponded to clusters of neuromelanin (NM). These NM-rich zones were distinct from the hypointense ventromedial regions with high iron pigments. Nigral T2* imaging at 7T can reflect the density of NM-containing neurons as the metal-bound NM macromolecules may decrease T2* values and cause hypointense signalling in T2* imaging at 7T. PMID:27596274

  7. Intensity inhomogeneity correction for magnetic resonance imaging of human brain at 7T

    SciTech Connect

    Uwano, Ikuko; Yamashita, Fumio; Higuchi, Satomi; Ito, Kenji; Sasaki, Makoto; Kudo, Kohsuke Goodwin, Jonathan; Harada, Taisuke; Ogawa, Akira

    2014-02-15

    Purpose: To evaluate the performance and efficacy for intensity inhomogeneity correction of various sequences of the human brain in 7T MRI using the extended version of the unified segmentation algorithm. Materials: Ten healthy volunteers were scanned with four different sequences (2D spin echo [SE], 3D fast SE, 2D fast spoiled gradient echo, and 3D time-of-flight) by using a 7T MRI system. Intensity inhomogeneity correction was performed using the “New Segment” module in SPM8 with four different values (120, 90, 60, and 30 mm) of full width at half maximum (FWHM) in Gaussian smoothness. The uniformity in signals in the entire white matter was evaluated using the coefficient of variation (CV); mean signal intensities between the subcortical and deep white matter were compared, and contrast between subcortical white matter and gray matter was measured. The length of the lenticulostriate (LSA) was measured on maximum intensity projection (MIP) images in the original and corrected images. Results: In all sequences, the CV decreased as the FWHM value decreased. The differences of mean signal intensities between subcortical and deep white matter also decreased with smaller FWHM values. The contrast between white and gray matter was maintained at all FWHM values. LSA length was significantly greater in corrected MIP than in the original MIP images. Conclusions: Intensity inhomogeneity in 7T MRI can be successfully corrected using SPM8 for various scan sequences.

  8. The Neuromelanin-related T2* Contrast in Postmortem Human Substantia Nigra with 7T MRI.

    PubMed

    Lee, Jae-Hyeok; Baek, Sun-Yong; Song, YoungKyu; Lim, Sujeong; Lee, Hansol; Nguyen, Minh Phuong; Kim, Eun-Joo; Huh, Gi Yeong; Chun, Se Young; Cho, HyungJoon

    2016-01-01

    High field magnetic resonance imaging (MRI)-based delineation of the substantia nigra (SN) and visualization of its inner cellular organization are promising methods for the evaluation of morphological changes associated with neurodegenerative diseases; however, corresponding MR contrasts must be matched and validated with quantitative histological information. Slices from two postmortem SN samples were imaged with a 7 Tesla (7T) MRI with T1 and T2* imaging protocols and then stained with Perl's Prussian blue, Kluver-Barrera, tyrosine hydroxylase, and calbindin immunohistochemistry in a serial manner. The association between T2* values and quantitative histology was investigated with a co-registration method that accounts for histology slice preparation. The ventral T2* hypointense layers between the SNr and the crus cerebri extended anteriorly to the posterior part of the crus cerebri, which demonstrates the difficulty with an MRI-based delineation of the SN. We found that the paramagnetic hypointense areas within the dorsolateral SN corresponded to clusters of neuromelanin (NM). These NM-rich zones were distinct from the hypointense ventromedial regions with high iron pigments. Nigral T2* imaging at 7T can reflect the density of NM-containing neurons as the metal-bound NM macromolecules may decrease T2* values and cause hypointense signalling in T2* imaging at 7T. PMID:27596274

  9. Analysis of motion disambiguation using multi-channel circular SAR

    NASA Astrophysics Data System (ADS)

    Fasih, Ahmed R.; Rossler, Carl W.; Ash, Joshua N.; Moses, Randolph L.

    2010-04-01

    Combining moving target indication (MTI) radar with synthetic aperture radar (SAR) is of great interest to radar specialists, in terms of improving multiple-target tracking in large, urban scenes. A major obstacle to such a merger are ambiguities induced by mution. Using statistical bounds we quantify the improvement of moving target localization with multi-channel SAR over single-channel SAR and the more traditional MTI technique of displaced phase center array (DPCA) processing. We show that the potential for substantial improvements in localization performance is borne out by practical estimators based on sparse reconstruction algorithms, whose performance approach statistical bounds, even under clutter. We also outline a parallelization scheme for the nonquadratic regularized sparse reconstruction technique to utilize clusters for processing large datasets.

  10. Coupling output of multichannel high power microwaves

    SciTech Connect

    Li Guolin; Shu Ting; Yuan Chengwei; Zhang Jun; Yang Jianhua; Jin Zhenxing; Yin Yi; Wu Dapeng; Zhu Jun; Ren Heming; Yang Jie

    2010-12-15

    The coupling output of multichannel high power microwaves is a promising technique for the development of high power microwave technologies, as it can enhance the output capacities of presently studied devices. According to the investigations on the spatial filtering method and waveguide filtering method, the hybrid filtering method is proposed for the coupling output of multichannel high power microwaves. As an example, a specific structure is designed for the coupling output of S/X/X band three-channel high power microwaves and investigated with the hybrid filtering method. In the experiments, a pulse of 4 GW X band beat waves and a pulse of 1.8 GW S band microwave are obtained.

  11. Coupling output of multichannel high power microwaves

    NASA Astrophysics Data System (ADS)

    Li, Guolin; Shu, Ting; Yuan, Chengwei; Zhang, Jun; Yang, Jianhua; Jin, Zhenxing; Yin, Yi; Wu, Dapeng; Zhu, Jun; Ren, Heming; Yang, Jie

    2010-12-01

    The coupling output of multichannel high power microwaves is a promising technique for the development of high power microwave technologies, as it can enhance the output capacities of presently studied devices. According to the investigations on the spatial filtering method and waveguide filtering method, the hybrid filtering method is proposed for the coupling output of multichannel high power microwaves. As an example, a specific structure is designed for the coupling output of S/X/X band three-channel high power microwaves and investigated with the hybrid filtering method. In the experiments, a pulse of 4 GW X band beat waves and a pulse of 1.8 GW S band microwave are obtained.

  12. 26 CFR 1.6049-7T - Market discount fraction reported with other financial information with respect to REMICs and...

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... Section 1.6049-7T Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) INCOME TAX (CONTINUED) INCOME TAXES (CONTINUED) Information Returns § 1.6049-7T Market discount fraction... 26 Internal Revenue 13 2011-04-01 2011-04-01 false Market discount fraction reported with...

  13. Complex and magnitude-only preprocessing of 2D and 3D BOLD fMRI data at 7 T.

    PubMed

    Barry, Robert L; Strother, Stephen C; Gore, John C

    2012-03-01

    A challenge to ultra high field functional magnetic resonance imaging is the predominance of noise associated with physiological processes unrelated to tasks of interest. This degradation in data quality may be partially reversed using a series of preprocessing algorithms designed to retrospectively estimate and remove the effects of these noise sources. However, such algorithms are routinely validated only in isolation, and thus consideration of their efficacies within realistic preprocessing pipelines and on different data sets is often overlooked. We investigate the application of eight possible combinations of three pseudo-complementary preprocessing algorithms - phase regression, Stockwell transform filtering, and retrospective image correction - to suppress physiological noise in 2D and 3D functional data at 7 T. The performance of each preprocessing pipeline was evaluated using data-driven metrics of reproducibility and prediction. The optimal preprocessing pipeline for both 2D and 3D functional data included phase regression, Stockwell transform filtering, and retrospective image correction. This result supports the hypothesis that a complex preprocessing pipeline is preferable to a magnitude-only pipeline, and suggests that functional magnetic resonance imaging studies should retain complex images and externally monitor subjects' respiratory and cardiac cycles so that these supplementary data may be used to retrospectively reduce noise and enhance overall data quality.

  14. Multichannel cochlear implants in partially ossified cochleas.

    PubMed

    Balkany, T; Gantz, B; Nadol, J B

    1988-01-01

    Deposition of bone within the fluid spaces of the cochlea is encountered commonly in cochlear implant candidates and previously has been considered a relative contraindication to the use of multichannel intracochlear electrodes. This contraindication has been based on possible mechanical difficulty with electrode insertion as well as uncertainty about the potential benefit of the multichannel device in the patient. Fifteen profoundly deaf patients with partial ossification of the basal turn of the cochlea received implants with long intracochlear electrodes (11, Nucleus; 1, University of California at San Francisco/Storz; and 3, Symbion/Inneraid). In 11 cases, ossification had been predicted preoperatively by computed tomographic scan. Electrodes were completely inserted in 14 patients, and partial insertion was accomplished in one patient. All patients currently are using their devices and nine of 12 postlingually deaf patients have achieved some degree of open-set speech discrimination. This series demonstrates that in experienced hands, insertion of long multichannel electrodes into partially ossified cochleas is possible and that results are similar to those achieved in patients who have nonossified cochleas. PMID:3140705

  15. State-space models for multichannel detection

    NASA Astrophysics Data System (ADS)

    Roman, J. R.; Davis, D. W.

    1993-07-01

    In multichannel identification and detection (or model-based multichannel detection) problems the parameters of a model are identified from the observed channel process and the identified model is used to facilitate the detection of a signal in the observe process. A model-based multichannel detection algorithm was developed in the context of an innovations-based detection algorithm (IBDA) formulation for surveillance radar system applications. The state space model class was adopted to model the vector channel process because it is more general than the time series model class used in most analyses to date. An IBDA methodology was developed based on the canonical correlations algorithm which for state-space model identification offers performance advantages over alternative techniques. A computer simulation was developed to validate the methodology and the algorithm, and to carry out performance assessments. Simulation results indicate that the algorithm is capable of discriminating between the null hypothesis (clutter plus noise) and the alternative hypothesis (signal plus clutter plus noise). In summary, the applicability of the approach to radar system problems was established.

  16. Element decoupling of 7T dipole body arrays by EBG metasurface structures: Experimental verification.

    PubMed

    Hurshkainen, Anna A; Derzhavskaya, Tatyana A; Glybovski, Stanislav B; Voogt, Ingmar J; Melchakova, Irina V; van den Berg, Cornelis A T; Raaijmakers, Alexander J E

    2016-08-01

    Metasurfaces are artificial electromagnetic boundaries or interfaces usually implemented as two-dimensional periodic structures with subwavelength periodicity and engineered properties of constituent unit cells. The electromagnetic bandgap (EBG) effect in metasurfaces prevents all surface modes from propagating in a certain frequency band. While metasurfaces provide a number of important applications in microwave antennas and antenna arrays, their features are also highly suitable for MRI applications. In this work we perform a proof-of-principle experiment to study finite structures based on mushroom-type EBG metasurfaces and employ them for suppression of inter-element coupling in dipole transceive array coils for body imaging at 7T. We firstly show experimentally that employment of mushroom structures leads to reduction of coupling between adjacent closely-spaced dipole antenna elements of a 7T transceive body array, which reduces scattering losses in neighboring channels. The studied setup consists of two active fractionated dipole antennas previously designed by the authors for body imaging at 7T. These are placed on top of a body-mimicking phantom and equipped with the manufactured finite-size periodic structure tuned to have EBG properties at the Larmor frequency of 298MHz. To improve the detection range of the B1+ field distribution of the top elements, four additional elements were positioned along the bottom side of the phantom. Bench measurements of a scattering matrix showed that coupling between the two top elements can be considerably reduced depending on the distance to the EBG structure. On the other hand, the measurements performed on a 7T MRI machine indicated redistribution of the B1+ field due to interaction between the dipoles with the structure. When the structure is located just over two closely spaced dipoles, one can reach a very high isolation improvement of -14dB accompanied by a strong field redistribution. In contrast, when put at a

  17. Element decoupling of 7 T dipole body arrays by EBG metasurface structures: Experimental verification

    NASA Astrophysics Data System (ADS)

    Hurshkainen, Anna A.; Derzhavskaya, Tatyana A.; Glybovski, Stanislav B.; Voogt, Ingmar J.; Melchakova, Irina V.; van den Berg, Cornelis A. T.; Raaijmakers, Alexander J. E.

    2016-08-01

    Metasurfaces are artificial electromagnetic boundaries or interfaces usually implemented as two-dimensional periodic structures with subwavelength periodicity and engineered properties of constituent unit cells. The electromagnetic bandgap (EBG) effect in metasurfaces prevents all surface modes from propagating in a certain frequency band. While metasurfaces provide a number of important applications in microwave antennas and antenna arrays, their features are also highly suitable for MRI applications. In this work we perform a proof-of-principle experiment to study finite structures based on mushroom-type EBG metasurfaces and employ them for suppression of inter-element coupling in dipole transceive array coils for body imaging at 7 T. We firstly show experimentally that employment of mushroom structures leads to reduction of coupling between adjacent closely-spaced dipole antenna elements of a 7 T transceive body array, which reduces scattering losses in neighboring channels. The studied setup consists of two active fractionated dipole antennas previously designed by the authors for body imaging at 7 T. These are placed on top of a body-mimicking phantom and equipped with the manufactured finite-size periodic structure tuned to have EBG properties at the Larmor frequency of 298 MHz. To improve the detection range of the B1 + field distribution of the top elements, four additional elements were positioned along the bottom side of the phantom. Bench measurements of a scattering matrix showed that coupling between the two top elements can be considerably reduced depending on the distance to the EBG structure. On the other hand, the measurements performed on a 7 T MRI machine indicated redistribution of the B1 + field due to interaction between the dipoles with the structure. When the structure is located just over two closely spaced dipoles, one can reach a very high isolation improvement of -14 dB accompanied by a strong field redistribution. In contrast, when put

  18. Element decoupling of 7T dipole body arrays by EBG metasurface structures: Experimental verification.

    PubMed

    Hurshkainen, Anna A; Derzhavskaya, Tatyana A; Glybovski, Stanislav B; Voogt, Ingmar J; Melchakova, Irina V; van den Berg, Cornelis A T; Raaijmakers, Alexander J E

    2016-08-01

    Metasurfaces are artificial electromagnetic boundaries or interfaces usually implemented as two-dimensional periodic structures with subwavelength periodicity and engineered properties of constituent unit cells. The electromagnetic bandgap (EBG) effect in metasurfaces prevents all surface modes from propagating in a certain frequency band. While metasurfaces provide a number of important applications in microwave antennas and antenna arrays, their features are also highly suitable for MRI applications. In this work we perform a proof-of-principle experiment to study finite structures based on mushroom-type EBG metasurfaces and employ them for suppression of inter-element coupling in dipole transceive array coils for body imaging at 7T. We firstly show experimentally that employment of mushroom structures leads to reduction of coupling between adjacent closely-spaced dipole antenna elements of a 7T transceive body array, which reduces scattering losses in neighboring channels. The studied setup consists of two active fractionated dipole antennas previously designed by the authors for body imaging at 7T. These are placed on top of a body-mimicking phantom and equipped with the manufactured finite-size periodic structure tuned to have EBG properties at the Larmor frequency of 298MHz. To improve the detection range of the B1+ field distribution of the top elements, four additional elements were positioned along the bottom side of the phantom. Bench measurements of a scattering matrix showed that coupling between the two top elements can be considerably reduced depending on the distance to the EBG structure. On the other hand, the measurements performed on a 7T MRI machine indicated redistribution of the B1+ field due to interaction between the dipoles with the structure. When the structure is located just over two closely spaced dipoles, one can reach a very high isolation improvement of -14dB accompanied by a strong field redistribution. In contrast, when put at a

  19. All-optical multi-channel wavelength conversion of Nyquist 16 QAM signal using a silicon waveguide.

    PubMed

    Long, Yun; Liu, Jun; Hu, Xiao; Wang, Andong; Zhou, Linjie; Zou, Kaiheng; Zhu, Yixiao; Zhang, Fan; Wang, Jian

    2015-12-01

    We experimentally demonstrate on-chip all-optical multi-channel wavelength conversion of Nyquist 16 ary quadrature amplitude modulation (16 QAM) signal in a silicon waveguide. The measured optical signal-to-noise ratio (OSNR) penalties of wavelength conversion are ∼2  dB. The observed constellations of converted idlers indicate favorable performance of silicon-waveguide-based multi-channel wavelength conversion. We also experimentally study and compare the phase-conjugated wavelength conversion by degenerate four-wave mixing (FWM) and transparent wavelength conversion by non-degenerate FWM in the silicon waveguide.

  20. Measurement of T1 of human arterial and venous blood at 7T

    PubMed Central

    Rane, S.; Gore, J.C.

    2012-01-01

    Techniques for measuring cerebral perfusion require accurate longitudinal relaxation (T1) of blood, a MRI parameter that is field dependent. T1 of arterial and venous human blood was measured at 7T using three different sources – pathology laboratory, blood bank and in vivo. The T1 of venous blood was measured from sealed samples from a pathology lab and in vivo. Samples from a blood bank were oxygenated and mixed to obtain different physiological concentrations of hematocrit and oxygenation. T1 relaxation times were estimated using a three-point fit to a simple inversion recovery equation. At 37° C, the T1 of blood at arterial pO2was 2.29 ± 0.1 s and 2.07 ± 0.12 at venous pO2. The in vivo T1 of venous blood, in three subjects, was slightly longer at 2.45 ± 0.11s. T1 of arterial and venous blood at 7T was measured and found to be significantly different. The T1 values were longer in vivo than in vitro. While the exact cause for the discrepancy is unknown, the additives in the blood samples, degradation during experiment, oxygenation differences, and the non-stagnant nature of blood in vivo could be potential contributors to the lower values of T1 in the venous samples. PMID:23102945

  1. High-Resolution Fast Spin Echo Imaging of the Human Brain at 4.7 T: Implementation and Sequence Characteristics

    PubMed Central

    Thomas, David L.; Vita, Enrico De; Roberts, Steven; Turner, Robert; Yousry, Tarek A.; Ordidge, Roger J.

    2007-01-01

    In this work, a number of important issues associated with fast spin echo (FSE) imaging of the human brain at 4.7 T are addressed. It is shown that FSE enables the acquisition of images with high resolution and good tissue contrast throughout the brain at high field strength. By employing an echo spacing (ES) of 22 ms, one can use large flip angle refocusing pulses (162°) and a low acquisition bandwidth (50 kHz) to maximize the signal-to-noise ratio (SNR). A new method of phase encode (PE) ordering (called “feathering”) designed to reduce image artifacts is described, and the contributions of RF (B1) inhomogeneity, different echo coherence pathways, and magnetization transfer (MT) to FSE signal intensity and contrast are investigated. B1 inhomogeneity is measured and its effect is shown to be relatively minor for high-field FSE, due to the self-compensating characteristics of the sequence. Thirty-four slice data sets (slice thickness = 2 mm; in-plane resolution = 0.469 mm; acquisition time = 11 min 20 s) from normal volunteers are presented, which allow visualization of brain anatomy in fine detail. This study demonstrates that high-field FSE produces images of the human brain with high spatial resolution, SNR, and tissue contrast, within currently prescribed power deposition guidelines. Magn Reson Med 51:1254-1264, 2004. PMID:15170847

  2. Asynchronous data readout system for multichannel ASIC

    NASA Astrophysics Data System (ADS)

    Ivanov, P. Y.; Atkin, E. V.

    2016-02-01

    The data readout system of multichannel data-driven ASIC, requiring high-speed (320 Mb/s) output data serialization is described. Its structure, based on a limited number of FIFO blocks, provides a lossless data transfer. The solution has been realized as a separate test IP block in the prototyped 8 channel ASIC, intended for the muon chamber of CBM experiment at FAIR. The block was developed for the UMC 0.18 μm MMRF CMOS process and prototyped via Europractice. Main parameters of the chip are given.

  3. Simple multifunction discriminator for multichannel triggers

    SciTech Connect

    Maier, M.R.

    1982-10-01

    A simple version of a multifunction timing discriminator using only two integrated circuits is presented. It can be configured as a leading edge, a constant fraction, a zero cross or a dual threshold timing discriminator. Since so few parts are used, it is well suited for building multichannel timing discriminators. Two versions of this circuit are described: a quadruple multifunction discriminator and an octal constant fraction trigger. The different compromises made in these units are discussed. Results for walk and jitter obtained with these are presented and possible improvements are disussed.

  4. Multichannel linear predictive coding of color images

    NASA Astrophysics Data System (ADS)

    Maragos, P. A.; Mersereau, R. M.; Schafer, R. W.

    This paper reports on a preliminary study of applying single-channel (scalar) and multichannel (vector) 2-D linear prediction to color image modeling and coding. Also, the novel idea of a multi-input single-output 2-D ADPCM coder is introduced. The results of this study indicate that texture information in multispectral images can be represented by linear prediction coefficients or matrices, whereas the prediction error conveys edge-information. Moreover, by using a single-channel edge-information the investigators obtained, from original color images of 24 bits/pixel, reconstructed images of good quality at information rates of 1 bit/pixel or less.

  5. FOMA: A Fast Optical Multichannel Analyzer

    NASA Astrophysics Data System (ADS)

    Haskovec, J. S.; Bramson, G.; Brooks, N. H.; Perry, M.

    1989-12-01

    A Fast Optical Multichannel Analyzer (FOMA) was built for spectroscopic measurements with fast time resolution on the DIII-D tokamak. The FOMA utilizes a linear photodiode array (RETICON RL 1024 SA) as the detector sensor. An external recharge switch and ultrafast operational amplifiers permit a readout time per pixel of 300 ns. In conjunction with standard CAMAC digitizer and timing modules, a readout time of 500 microns is achieved for the full 1024-element array. Data acquired in bench tests and in actual spectroscopic measurements on the DIII-D tokamak is presented to illustrate the camera's capability.

  6. A low power Multi-Channel Analyzer

    SciTech Connect

    Anderson, G.A.; Brackenbush, L.W.

    1993-06-01

    The instrumentation used in nuclear spectroscopy is generally large, is not portable, and requires a lot of power. Key components of these counting systems are the computer and the Multi-Channel Analyzer (MCA). To assist in performing measurements requiring portable systems, a small, very low power MCA has been developed at Pacific Northwest Laboratory (PNL). This MCA is interfaced with a Hewlett Packard palm top computer for portable applications. The MCA can also be connected to an IBM/PC for data storage and analysis. In addition, a real-time time display mode allows the user to view the spectra as they are collected.

  7. MULTI-CHANNEL PULSE HEIGHT ANALYZER

    DOEpatents

    Boyer, K.; Johnstone, C.W.

    1958-11-25

    An improved multi-channel pulse height analyzer of the type where the device translates the amplitude of each pulse into a time duration electrical quantity which is utilized to control the length of a train of pulses forwarded to a scaler is described. The final state of the scaler for any one train of pulses selects the appropriate channel in a magnetic memory in which an additional count of one is placed. The improvement consists of a storage feature for storing a signal pulse so that in many instances when two signal pulses occur in rapid succession, the second pulse is preserved and processed at a later time.

  8. Multichannel euv spectroscopy of high temperature plasmas

    SciTech Connect

    Fonck, R.J.

    1983-11-01

    Spectroscopy of magnetically confined high temperature plasmas in the visible through x-ray spectral ranges deals primarily with the study of impurity line radiation or continuum radiation. Detailed knowledge of absolute intensities, temporal behavior, and spatial distributions of the emitted radiation is desired. As tokamak facilities become more complex, larger, and less accessible, there has been an increased emphasis on developing new instrumentation to provide such information in a minimum number of discharges. The availability of spatially-imaging detectors for use in the vacuum ultraviolet region (especially the intensified photodiode array) has generated the development of a variety of multichannel spectrometers for applications on tokamak facilities.

  9. Multichannel framework for singular quantum mechanics

    NASA Astrophysics Data System (ADS)

    Camblong, Horacio E.; Epele, Luis N.; Fanchiotti, Huner; García Canal, Carlos A.; Ordóñez, Carlos R.

    2014-01-01

    A multichannel S-matrix framework for singular quantum mechanics (SQM) subsumes the renormalization and self-adjoint extension methods and resolves its boundary-condition ambiguities. In addition to the standard channel accessible to a distant ("asymptotic") observer, one supplementary channel opens up at each coordinate singularity, where local outgoing and ingoing singularity waves coexist. The channels are linked by a fully unitary S-matrix, which governs all possible scenarios, including cases with an apparent nonunitary behavior as viewed from asymptotic distances.

  10. Multichannel image regularization using anisotropic geodesic filtering

    SciTech Connect

    Grazzini, Jacopo A

    2010-01-01

    This paper extends a recent image-dependent regularization approach introduced in aiming at edge-preserving smoothing. For that purpose, geodesic distances equipped with a Riemannian metric need to be estimated in local neighbourhoods. By deriving an appropriate metric from the gradient structure tensor, the associated geodesic paths are constrained to follow salient features in images. Following, we design a generalized anisotropic geodesic filter; incorporating not only a measure of the edge strength, like in the original method, but also further directional information about the image structures. The proposed filter is particularly efficient at smoothing heterogeneous areas while preserving relevant structures in multichannel images.

  11. Planar quadrature RF transceiver design using common-mode differential-mode (CMDM) transmission line method for 7T MR imaging.

    PubMed

    Li, Ye; Yu, Baiying; Pang, Yong; Vigneron, Daniel B; Zhang, Xiaoliang

    2013-01-01

    The use of quadrature RF magnetic fields has been demonstrated to be an efficient method to reduce transmit power and to increase the signal-to-noise (SNR) in magnetic resonance (MR) imaging. The goal of this project was to develop a new method using the common-mode and differential-mode (CMDM) technique for compact, planar, distributed-element quadrature transmit/receive resonators for MR signal excitation and detection and to investigate its performance for MR imaging, particularly, at ultrahigh magnetic fields. A prototype resonator based on CMDM method implemented by using microstrip transmission line was designed and fabricated for 7T imaging. Both the common mode (CM) and the differential mode (DM) of the resonator were tuned and matched at 298MHz independently. Numerical electromagnetic simulation was performed to verify the orthogonal B1 field direction of the two modes of the CMDM resonator. Both workbench tests and MR imaging experiments were carried out to evaluate the performance. The intrinsic decoupling between the two modes of the CMDM resonator was demonstrated by the bench test, showing a better than -36 dB transmission coefficient between the two modes at resonance frequency. The MR images acquired by using each mode and the images combined in quadrature showed that the CM and DM of the proposed resonator provided similar B1 coverage and achieved SNR improvement in the entire region of interest. The simulation and experimental results demonstrate that the proposed CMDM method with distributed-element transmission line technique is a feasible and efficient technique for planar quadrature RF coil design at ultrahigh fields, providing intrinsic decoupling between two quadrature channels and high frequency capability. Due to its simple and compact geometry and easy implementation of decoupling methods, the CMDM quadrature resonator can possibly be a good candidate for design blocks in multichannel RF coil arrays.

  12. Magnetic resonance imaging of the inner ear by using a hybrid radiofrequency coil at 7 T

    NASA Astrophysics Data System (ADS)

    Kim, Kyoung-Nam; Heo, Phil; Kim, Young-Bo; Han, Gyu-Cheol

    2015-01-01

    Visualization of the membranous structures of the inner ear has been limited to the detection of the normal fluid signal intensity within the bony labyrinth by using magnetic resonance imaging (MRI) equipped with a 1.5 Tesla (T) magnet. High-field (HF) MRI has been available for more than a decade, and numerous studies have documented its significant advantages over conventional MRI with regards to its use in basic scientific research and routine clinical assessments. No previous studies of the inner ear by using HF MRI have been reported, in part because high-quality resolution of mastoid pneumatization is challenging due to artifacts generated in the HF environment and insufficient performance of radiofrequency (RF) coils. Therefore, a hybrid RF coil with integrated circuitry was developed at 7 T and was targeted for anatomical imaging to achieve a high resolution image of the structure of the human inner ear, excluding the bony portion. The inner-ear's structure is composed of soft tissues containing hydrogen ions and includes the membranous labyrinth, endolymphatic space, perilymphatic space, and cochlear-vestibular nerves. Visualization of the inner-ear's anatomy was performed in-vivo with a custom-designed hybrid RF coil and a specific imaging protocol based on an interpolated breath-held examination sequence. The comparative signal intensity value at 30-mm away from the phantom side was 88% higher for the hybrid RF coil and 24% higher for the 8-channel transmit/receive (Tx/Rx) coil than for the commercial birdcage coil. The optimized MRI protocol employed a hybrid RF coil because it enabled high-resolution imaging of the inner-ear's anatomy and accurate mapping of structures including the cochlea and the semicircular canals. These results indicate that 7 T MRI achieves high spatial resolution visualization of the inner-ear's anatomy. Therefore, MRI imaging using a hybrid RF coil at 7 T could provide a powerful tool for clinical investigations of petrous

  13. Nineteen-Channel Receive Array and Four-Channel Transmit Array Coil for Cervical Spinal Cord Imaging at 7T

    PubMed Central

    Zhao, Wei; Cohen-Adad, Julien; Polimeni, Jonathan R.; Keil, Boris; Guerin, Bastien; Setsompop, Kawin; Serano, Peter; Mareyam, Azma; Hoecht, Philipp; Wald, Lawrence L.

    2016-01-01

    Purpose To design and validate a radiofrequency (RF) array coil for cervical spinal cord imaging at 7T. Methods A 19-channel receive array with a four-channel transmit array was developed on a close-fitting coil former at 7T. Transmit efficiency and specific absorption rate were evaluated in a B1+ mapping study and an electromagnetic model. Receive signal-to-noise ratio (SNR) and noise amplification for parallel imaging were evaluated and compared with a commercial 3T 19-channel head–neck array and a 7T four-channel spine array. The performance of the array was qualitatively demonstrated in human volunteers using high-resolution imaging (down to 300 μm in-plane). Results The transmit and receive arrays showed good bench performance. The SNR was approximately 4.2-fold higher in the 7T receive array at the location of the cord with respect to the 3T coil. The g-factor results showed an additional acceleration was possible with the 7T array. In vivo imaging was feasible and showed high SNR and tissue contrast. Conclusion The highly parallel transmit and receive arrays were demonstrated to be fit for spinal cord imaging at 7T. The high sensitivity of the receive coil combined with ultra-high field will likely improve investigations of microstructure and tissue segmentation in the healthy and pathological spinal cord. PMID:23963998

  14. Myelin contrast across lamina at 7T, ex-vivo and in-vivo dataset.

    PubMed

    Fracasso, Alessio; van Veluw, Susanne J; Visser, Fredy; Luijten, Peter R; Spliet, Wim; Zwanenburg, Jaco J M; Dumoulin, Serge O; Petridou, Natalia

    2016-09-01

    In this article we report the complete data obtained in-vivo for the paper: "Lines of Baillarger in vivo and ex-vivo: myelin contrast across lamina at 7T MRI and histology" (Fracasso et al., 2015) [1]. Single participant data (4 participants) from the occipital lobe acquisition are reported for axial, coronal and sagittal slices; early visual area functional localization and laminar profiles are reported. Data from whole brain images are reported and described (5 participants), for axial, coronal and sagittal slices. Laminar profiles from occipital, parietal and frontal lobes are reported. The data reported in this manuscript complements the paper (Fracasso et al., 2015) [1] by providing the full set of results from the complete pool of participants, on a single-participant basis. Moreover, we provide histological images from the ex-vivo sample reported in Fracasso et al. (2015) [1]. PMID:27508254

  15. A radiofrequency coil configuration for imaging the human vertebral column at 7 T

    NASA Astrophysics Data System (ADS)

    Vossen, M.; Teeuwisse, W.; Reijnierse, M.; Collins, C. M.; Smith, N. B.; Webb, A. G.

    2011-02-01

    We describe the design and testing of a quadrature transmit, eight-channel receive array RF coil configuration for the acquisition of images of the entire human spinal column at 7 T. Imaging parameters were selected to enable data acquisition in a clinically relevant scan time. Large field-of-view (FOV) scanning enabled sagittal imaging of the spine in two or three-stations, depending upon the height of the volunteer, with a total scan time of between 10 and 15 min. A total of 10 volunteers have been scanned, with results presented for the three subjects spanning the range of heights and weights, namely one female (1.6 m, 50 kg), one average male (1.8 m, 70 kg), and one large male (1.9 m, 100 kg).

  16. A 7 T Pulsed Magnetic Field Generator for Magnetized Laser Plasma Experiments

    NASA Astrophysics Data System (ADS)

    Hu, Guangyue; Liang, Yihan; Song, Falun; Yuan, Peng; Wang, Yulin; Zhao, Bin; Zheng, Jian

    2015-02-01

    A pulsed magnetic field generator was developed to study the effect of a magnetic field on the evolution of a laser-generated plasma. A 40 kV pulsed power system delivered a fast (~230 ns), 55 kA current pulse into a single-turn coil surrounding the laser target, using a capacitor bank of 200 nF, a laser-triggered switch and a low-impedance strip transmission line. A one-dimensional uniform 7 T pulsed magnetic field was created using a Helmholtz coil pair with a 6 mm diameter. The pulsed magnetic field was controlled to take effect synchronously with a nanosecond heating laser beam, a femtosecond probing laser beam and an optical Intensified Charge Coupled Device (ICCD) detector. The preliminary experiments demonstrate bifurcation and focusing of plasma expansion in a transverse magnetic field.

  17. A Switched-Mode Breast Coil for 7 T MRI Using Forced-Current Excitation

    PubMed Central

    Bosshard, John C.; Rispoli, Joseph V.; Dimitrov, Ivan E.; Cheshkov, Sergey; McDougall, Mary Preston; Malloy, Craig; Wright, Steven M.

    2015-01-01

    In high-field magnetic resonance imaging, the radio frequency wavelength within the human body is comparable to anatomical dimensions, resulting in B1 inhomogeneity and nonuniform sensitivity patterns. Thus, this relatively short wavelength presents engineering challenges for RF coil design. In this study, a bilateral breast coil for 1H imaging at 7 T was designed and constructed using forced-current excitation. By forcing equal current through the coil elements, we reduce the effects of coupling between the elements to simplify tuning and to ensure a uniform field across both breasts. To combine the benefits of the higher power efficiency of a unilateral coil with the bilateral coverage of a bilateral coil, a switching circuit was implemented to allow the coil to be reconfigured for imaging the left, right, or both breasts. PMID:25706501

  18. Myelin contrast across lamina at 7T, ex-vivo and in-vivo dataset.

    PubMed

    Fracasso, Alessio; van Veluw, Susanne J; Visser, Fredy; Luijten, Peter R; Spliet, Wim; Zwanenburg, Jaco J M; Dumoulin, Serge O; Petridou, Natalia

    2016-09-01

    In this article we report the complete data obtained in-vivo for the paper: "Lines of Baillarger in vivo and ex-vivo: myelin contrast across lamina at 7T MRI and histology" (Fracasso et al., 2015) [1]. Single participant data (4 participants) from the occipital lobe acquisition are reported for axial, coronal and sagittal slices; early visual area functional localization and laminar profiles are reported. Data from whole brain images are reported and described (5 participants), for axial, coronal and sagittal slices. Laminar profiles from occipital, parietal and frontal lobes are reported. The data reported in this manuscript complements the paper (Fracasso et al., 2015) [1] by providing the full set of results from the complete pool of participants, on a single-participant basis. Moreover, we provide histological images from the ex-vivo sample reported in Fracasso et al. (2015) [1].

  19. Fourier-domain multichannel autofocus for synthetic aperture radar.

    PubMed

    Liu, Kuang-Hung; Munson, David C

    2011-12-01

    Synthetic aperture radar (SAR) imaging suffers from image focus degradation in the presence of phase errors in the received signal due to unknown platform motion or signal propagation delays. We present a new autofocus algorithm, termed Fourier-domain multichannel autofocus (FMCA), that is derived under a linear algebraic framework, allowing the SAR image to be focused in a noniterative fashion. Motivated by the mutichannel autofocus (MCA) approach, the proposed autofocus algorithm invokes the assumption of a low-return region, which generally is provided within the antenna sidelobes. Unlike MCA, FMCA works with the collected polar Fourier data directly and is capable of accommodating wide-angle monostatic SAR and bistatic SAR scenarios. Most previous SAR autofocus algorithms rely on the prior assumption that radar's range of look angles is small so that the phase errors can be modeled as varying along only one dimension in the collected Fourier data. And, in some cases, implicit assumptions are made regarding the SAR scene. Performance of such autofocus algorithms degrades if the assumptions are not satisfied. The proposed algorithm has the advantage that it does not require prior assumptions about the range of look angles, nor characteristics of the scene. PMID:21606028

  20. Fourier-domain multichannel autofocus for synthetic aperture radar.

    PubMed

    Liu, Kuang-Hung; Munson, David C

    2011-12-01

    Synthetic aperture radar (SAR) imaging suffers from image focus degradation in the presence of phase errors in the received signal due to unknown platform motion or signal propagation delays. We present a new autofocus algorithm, termed Fourier-domain multichannel autofocus (FMCA), that is derived under a linear algebraic framework, allowing the SAR image to be focused in a noniterative fashion. Motivated by the mutichannel autofocus (MCA) approach, the proposed autofocus algorithm invokes the assumption of a low-return region, which generally is provided within the antenna sidelobes. Unlike MCA, FMCA works with the collected polar Fourier data directly and is capable of accommodating wide-angle monostatic SAR and bistatic SAR scenarios. Most previous SAR autofocus algorithms rely on the prior assumption that radar's range of look angles is small so that the phase errors can be modeled as varying along only one dimension in the collected Fourier data. And, in some cases, implicit assumptions are made regarding the SAR scene. Performance of such autofocus algorithms degrades if the assumptions are not satisfied. The proposed algorithm has the advantage that it does not require prior assumptions about the range of look angles, nor characteristics of the scene.

  1. Fully adiabatic 31P 2D-CSI with reduced chemical shift displacement error at 7 T--GOIA-1D-ISIS/2D-CSI.

    PubMed

    Chmelík, M; Kukurová, I Just; Gruber, S; Krššák, M; Valkovič, L; Trattnig, S; Bogner, W

    2013-05-01

    A fully adiabatic phosphorus (31P) two-dimensional (2D) chemical shift spectroscopic imaging sequence with reduced chemical shift displacement error for 7 T, based on 1D-image-selected in vivo spectroscopy, combined with 2D-chemical shift spectroscopic imaging selection, was developed. Slice-selective excitation was achieved by a spatially selective broadband GOIA-W(16,4) inversion pulse with an interleaved subtraction scheme before nonselective adiabatic excitation, and followed by 2D phase encoding. The use of GOIA-W(16,4) pulses (bandwidth 4.3-21.6 kHz for 10-50 mm slices) reduced the chemical shift displacement error in the slice direction ∼1.5-7.7 fold, compared to conventional 2D-chemical shift spectroscopic imaging with Sinc3 selective pulses (2.8 kHz). This reduction was experimentally demonstrated with measurements of an MR spectroscopy localization phantom and with experimental evaluation of pulse profiles. In vivo experiments in clinically acceptable measurement times were demonstrated in the calf muscle (nominal voxel volume, 5.65 ml in 6 min 53 s), brain (10 ml, 6 min 32 s), and liver (8.33 ml, 8 min 14 s) of healthy volunteers at 7 T. High reproducibility was found in the calf muscle at 7 T. In combination with adiabatic excitation, this sequence is insensitive to the B1 inhomogeneities associated with surface coils. This sequence, which is termed GOIA-1D-ISIS/2D-CSI (goISICS), has the potential to be applied in both clinical research and in the clinical routine.

  2. Fault analysis of multichannel spacecraft power systems

    NASA Technical Reports Server (NTRS)

    Dugal-Whitehead, Norma R.; Lollar, Louis F.

    1990-01-01

    The NASA Marshall Space Flight Center proposes to implement computer-controlled fault injection into an electrical power system breadboard to study the reactions of the various control elements of this breadboard. Elements under study include the remote power controllers, the algorithms in the control computers, and the artificially intelligent control programs resident in this breadboard. To this end, a study of electrical power system faults is being performed to yield a list of the most common power system faults. The results of this study will be applied to a multichannel high-voltage DC spacecraft power system called the large autonomous spacecraft electrical power system (LASEPS) breadboard. The results of the power system fault study and the planned implementation of these faults into the LASEPS breadboard are described.

  3. Multichannel quantum defect theory for polar molecules

    NASA Astrophysics Data System (ADS)

    Elfimov, Sergei V.; Dorofeev, Dmitrii L.; Zon, Boris A.

    2014-02-01

    Our work is devoted to developing a general approach for nonpenetrating Rydberg states of polar molecules. We propose a method to estimate the accuracy of calculation of their wave functions and quantum defects. Basing on this method we estimate the accuracy of Born-Oppenheimer (BO) and inverse Born-Oppenheimer (IBO) approximations for these states. This estimation enables us to determine the space and energy regions where BO and IBO approximations are valid. It depends on the interplay between l coupling (due to dipole potential of the core) and l uncoupling (due to rotation the core). Next we consider the intermediate region where both BO and IBO are not valid. For this intermediate region we propose a modification of Fano's multichannel quantum defect theory to match BO and IBO wave functions and show that it gives more reliable results. They are demonstrated on the example of SO molecule.

  4. A cryogenic multichannel electronically scanned pressure module

    NASA Technical Reports Server (NTRS)

    Shams, Qamar A.; Fox, Robert L.; Adcock, Edward E.; Kahng, Seun K.

    1992-01-01

    Consideration is given to a cryogenic multichannel electronically scanned pressure (ESP) module developed and tested over an extended temperature span from -184 to +50 C and a pressure range of 0 to 5 psig. The ESP module consists of 32 pressure sensor dice, four analog 8 differential-input multiplexers, and an amplifier circuit, all of which are packaged in a physical volume of 2 x 1 x 5/8 in with 32 pressure and two reference ports. Maximum nonrepeatability is measured at 0.21 percent of full-scale output. The ESP modules have performed consistently well over 15 times over the above temperature range and continue to work without any sign of degradation. These sensors are also immune to repeated thermal shock tests over a temperature change of 220 C/sec.

  5. Photonic generation for multichannel THz wireless communication.

    PubMed

    Shams, Haymen; Fice, Martyn J; Balakier, Katarzyna; Renaud, Cyril C; van Dijk, Frédéric; Seeds, Alwyn J

    2014-09-22

    We experimentally demonstrate photonic generation of a multichannel THz wireless signal at carrier frequency 200 GHz, with data rate up to 75 Gbps in QPSK modulation format, using an optical heterodyne technique and digital coherent detection. BER measurements were carried out for three subcarriers each modulated with 5 Gbaud QPSK or for two subcarriers modulated with 10 Gbaud QPSK, giving a total speed of 30 Gbps or 40 Gbps, respectively. The system evaluation was also performed with three subcarriers modulated with 12.5 Gbaud QPSK (75 Gbps total) without and with 40 km fibre transmission. The proposed system enhances the capacity of high-speed THz wireless transmission by using spectrally efficient modulated subcarriers spaced at the baud rate. This approach increases the overall transmission capacity and reduces the bandwidth requirement for electronic devices.

  6. A gradient in cortical pathology in multiple sclerosis by in vivo quantitative 7 T imaging.

    PubMed

    Mainero, Caterina; Louapre, Céline; Govindarajan, Sindhuja T; Giannì, Costanza; Nielsen, A Scott; Cohen-Adad, Julien; Sloane, Jacob; Kinkel, Revere P

    2015-04-01

    We used a surface-based analysis of T2* relaxation rates at 7 T magnetic resonance imaging, which allows sampling quantitative T2* throughout the cortical width, to map in vivo the spatial distribution of intracortical pathology in multiple sclerosis. Ultra-high resolution quantitative T2* maps were obtained in 10 subjects with clinically isolated syndrome/early multiple sclerosis (≤ 3 years disease duration), 18 subjects with relapsing-remitting multiple sclerosis (≥ 4 years disease duration), 13 subjects with secondary progressive multiple sclerosis, and in 17 age-matched healthy controls. Quantitative T2* maps were registered to anatomical cortical surfaces for sampling T2* at 25%, 50% and 75% depth from the pial surface. Differences in laminar quantitative T2* between each patient group and controls were assessed using general linear model (P < 0.05 corrected for multiple comparisons). In all 41 multiple sclerosis cases, we tested for associations between laminar quantitative T2*, neurological disability, Multiple Sclerosis Severity Score, cortical thickness, and white matter lesions. In patients, we measured, T2* in intracortical lesions and in the intracortical portion of leukocortical lesions visually detected on 7 T scans. Cortical lesional T2* was compared with patients' normal-appearing cortical grey matter T2* (paired t-test) and with mean cortical T2* in controls (linear regression using age as nuisance factor). Subjects with multiple sclerosis exhibited relative to controls, independent from cortical thickness, significantly increased T2*, consistent with cortical myelin and iron loss. In early disease, T2* changes were focal and mainly confined at 25% depth, and in cortical sulci. In later disease stages T2* changes involved deeper cortical laminae, multiple cortical areas and gyri. In patients, T2* in intracortical and leukocortical lesions was increased compared with normal-appearing cortical grey matter (P < 10(-10) and P < 10(-7)), and mean

  7. Multichannel SAR Interferometry via Classical and Bayesian Estimation Techniques

    NASA Astrophysics Data System (ADS)

    Budillon, Alessandra; Ferraiuolo, Giancarlo; Pascazio, Vito; Schirinzi, Gilda

    2005-12-01

    Some multichannel synthetic aperture radar interferometric configurations are analyzed. Both across-track and along-track interferometric systems, allowing to recover the height profile of the ground or the moving target radial velocities, respectively, are considered. The joint use of multichannel configurations, which can be either multifrequency or multi-baseline, and of classical or Bayesian statistical estimation techniques allows to obtain very accurate solutions and to overcome the limitations due to the presence of ambiguous solutions, intrinsic in the single-channel configurations. The improved performance of the multichannel-based methods with respect to the corresponding single-channel ones has been tested with numerical experiments on simulated data.

  8. Detection of volume loss in hippocampal layers in Alzheimer's disease using 7 T MRI: a feasibility study.

    PubMed

    Boutet, Claire; Chupin, Marie; Lehéricy, Stéphane; Marrakchi-Kacem, Linda; Epelbaum, Stéphane; Poupon, Cyril; Wiggins, Christopher; Vignaud, Alexandre; Hasboun, Dominique; Defontaines, Bénédicte; Hanon, Olivier; Dubois, Bruno; Sarazin, Marie; Hertz-Pannier, Lucie; Colliot, Olivier

    2014-01-01

    In Alzheimer's disease (AD), the hippocampus is an early site of tau pathology and neurodegeneration. Histological studies have shown that lesions are not uniformly distributed within the hippocampus. Moreover, alterations of different hippocampal layers may reflect distinct pathological processes. 7 T MRI dramatically improves the visualization of hippocampal subregions and layers. In this study, we aimed to assess whether 7 T MRI can detect volumetric changes in hippocampal layers in vivo in patients with AD. We studied four AD patients and seven control subjects. MR images were acquired using a whole-body 7 T scanner with an eight channel transmit-receive coil. Hippocampal subregions were manually segmented from coronal T2*-weighted gradient echo images with 0.3 × 0.3 × 1.2 mm3 resolution using a protocol that distinguishes between layers richer or poorer in neuronal bodies. Five subregions were segmented in the region of the hippocampal body: alveus, strata radiatum, lacunosum and moleculare (SRLM) of the cornu Ammonis (CA), hilum, stratum pyramidale of CA and stratum pyramidale of the subiculum. We found strong bilateral reductions in the SRLM of the cornu Ammonis and in the stratum pyramidale of the subiculum (p < 0.05), with average cross-sectional area reductions ranging from -29% to -49%. These results show that it is possible to detect volume loss in distinct hippocampal layers using segmentation of 7 T MRI. 7 T MRI-based segmentation is a promising tool for AD research.

  9. High-quality permanent draft genome sequence of the extremely osmotolerant diphenol degrading bacterium Halotalea alkalilenta AW-7T, and emended description of the genus Halotalea

    SciTech Connect

    Ntougias, Spyridon; Lapidus, Alla; Copeland, Alex; Reddy, T. B. K.; Pati, Amrita; Ivanova, Natalia N.; Markowitz, Victor M.; Klenk, Hans-Peter; Woyke, Tanja; Fasseas, Constantinos; Kyrpides, Nikos C.; Zervakis, Georgios I.

    2015-08-13

    Members of the genus Halotalea (family Halomonadaceae) are of high significance since they can tolerate the greatest glucose and maltose concentrations ever reported for known bacteria and are involved in the degradation of industrial effluents. Here, the characteristics and the permanent-draft genome sequence and annotation of Halotalea alkalilenta AW-7T are described. The microorganism was sequenced as a part of the Genomic Encyclopedia of Type Strains, Phase I: the one thousand microbial genomes (KMG) project at the DOE Joint Genome Institute, and it is the only strain within the genus Halotalea having its genome sequenced. The genome is 4,467,826 bp long and consists of 40 scaffolds with 64.62 % average GC content. A total of 4,104 genes were predicted, comprising of 4,028 protein-coding and 76 RNA genes. Most protein-coding genes (87.79 %) were assigned to a putative function. Halotalea alkalilenta AW-7T encodes the catechol and protocatechuate degradation to β-ketoadipate via the β-ketoadipate and protocatechuate ortho-cleavage degradation pathway, and it possesses the genetic ability to detoxify fluoroacetate, cyanate and acrylonitrile. Lastly, an emended description of the genus Halotalea Ntougias et al. 2007 is also provided in order to describe the delayed fermentation ability of the type strain.

  10. High-quality permanent draft genome sequence of the extremely osmotolerant diphenol degrading bacterium Halotalea alkalilenta AW-7T, and emended description of the genus Halotalea

    DOE PAGES

    Ntougias, Spyridon; Lapidus, Alla; Copeland, Alex; Reddy, T. B. K.; Pati, Amrita; Ivanova, Natalia N.; Markowitz, Victor M.; Klenk, Hans-Peter; Woyke, Tanja; Fasseas, Constantinos; et al

    2015-08-13

    Members of the genus Halotalea (family Halomonadaceae) are of high significance since they can tolerate the greatest glucose and maltose concentrations ever reported for known bacteria and are involved in the degradation of industrial effluents. Here, the characteristics and the permanent-draft genome sequence and annotation of Halotalea alkalilenta AW-7T are described. The microorganism was sequenced as a part of the Genomic Encyclopedia of Type Strains, Phase I: the one thousand microbial genomes (KMG) project at the DOE Joint Genome Institute, and it is the only strain within the genus Halotalea having its genome sequenced. The genome is 4,467,826 bp longmore » and consists of 40 scaffolds with 64.62 % average GC content. A total of 4,104 genes were predicted, comprising of 4,028 protein-coding and 76 RNA genes. Most protein-coding genes (87.79 %) were assigned to a putative function. Halotalea alkalilenta AW-7T encodes the catechol and protocatechuate degradation to β-ketoadipate via the β-ketoadipate and protocatechuate ortho-cleavage degradation pathway, and it possesses the genetic ability to detoxify fluoroacetate, cyanate and acrylonitrile. Lastly, an emended description of the genus Halotalea Ntougias et al. 2007 is also provided in order to describe the delayed fermentation ability of the type strain.« less

  11. High-quality permanent draft genome sequence of the extremely osmotolerant diphenol degrading bacterium Halotalea alkalilenta AW-7(T), and emended description of the genus Halotalea.

    PubMed

    Ntougias, Spyridon; Lapidus, Alla; Copeland, Alex; Reddy, T B K; Pati, Amrita; Ivanova, Natalia N; Markowitz, Victor M; Klenk, Hans-Peter; Woyke, Tanja; Fasseas, Constantinos; Kyrpides, Nikos C; Zervakis, Georgios I

    2015-01-01

    Members of the genus Halotalea (family Halomonadaceae) are of high significance since they can tolerate the greatest glucose and maltose concentrations ever reported for known bacteria and are involved in the degradation of industrial effluents. Here, the characteristics and the permanent-draft genome sequence and annotation of Halotalea alkalilenta AW-7(T) are described. The microorganism was sequenced as a part of the Genomic Encyclopedia of Type Strains, Phase I: the one thousand microbial genomes (KMG) project at the DOE Joint Genome Institute, and it is the only strain within the genus Halotalea having its genome sequenced. The genome is 4,467,826 bp long and consists of 40 scaffolds with 64.62 % average GC content. A total of 4,104 genes were predicted, comprising of 4,028 protein-coding and 76 RNA genes. Most protein-coding genes (87.79 %) were assigned to a putative function. Halotalea alkalilenta AW-7(T) encodes the catechol and protocatechuate degradation to β-ketoadipate via the β-ketoadipate and protocatechuate ortho-cleavage degradation pathway, and it possesses the genetic ability to detoxify fluoroacetate, cyanate and acrylonitrile. An emended description of the genus Halotalea Ntougias et al. 2007 is also provided in order to describe the delayed fermentation ability of the type strain. PMID:26380640

  12. Cardiac and respiratory double self-gated cine MRI in the mouse at 7 T.

    PubMed

    Hiba, Bassem; Richard, Nathalie; Janier, Marc; Croisille, Pierre

    2006-03-01

    ECG-gated cardiac MRI in the mouse is hindered by many technical difficulties in ECG signal recording inside static and variable high magnetic scanner fields. The present study proposes an alternative robust method of acquiring auto-gated cardiac and respiratory cine images in mouse heart. In our approach, a motion synchronization signal is extracted from the echo peak MR signal of a non-triggered radial acquisition. This signal is then used for both cardiac and respiratory retrospective gating before cine image reconstruction. Highly asymmetric echoes were acquired to achieve the radial k-space sampling in order to avoid radial acquisition related artifacts and to increase auto-gating robustness. In vivo experiments demonstrated the feasibility and robustness of self-gated cine-MRI in the mouse heart at 7T. The signal-to-noise and contrast-to-noise ratios of the self-gated and ECG-gated images were comparable, all parameters being equal. Magn Reson Med, 2006. (c) 2006 Wiley-Liss, Inc. PMID:16463350

  13. Cortical depth dependent functional responses in humans at 7T: improved specificity with 3D GRASE.

    PubMed

    De Martino, Federico; Zimmermann, Jan; Muckli, Lars; Ugurbil, Kamil; Yacoub, Essa; Goebel, Rainer

    2013-01-01

    Ultra high fields (7T and above) allow functional imaging with high contrast-to-noise ratios and improved spatial resolution. This, along with improved hardware and imaging techniques, allow investigating columnar and laminar functional responses. Using gradient-echo (GE) (T2* weighted) based sequences, layer specific responses have been recorded from human (and animal) primary visual areas. However, their increased sensitivity to large surface veins potentially clouds detecting and interpreting layer specific responses. Conversely, spin-echo (SE) (T2 weighted) sequences are less sensitive to large veins and have been used to map cortical columns in humans. T2 weighted 3D GRASE with inner volume selection provides high isotropic resolution over extended volumes, overcoming some of the many technical limitations of conventional 2D SE-EPI, whereby making layer specific investigations feasible. Further, the demonstration of columnar level specificity with 3D GRASE, despite contributions from both stimulated echoes and conventional T2 contrast, has made it an attractive alternative over 2D SE-EPI. Here, we assess the spatial specificity of cortical depth dependent 3D GRASE functional responses in human V1 and hMT by comparing it to GE responses. In doing so we demonstrate that 3D GRASE is less sensitive to contributions from large veins in superficial layers, while showing increased specificity (functional tuning) throughout the cortex compared to GE.

  14. Intracortical myelination in musicians with absolute pitch: Quantitative morphometry using 7-T MRI.

    PubMed

    Kim, Seung-Goo; Knösche, Thomas R

    2016-10-01

    Absolute pitch (AP) is known as the ability to recognize and label the pitch chroma of a given tone without external reference. Known brain structures and functions related to AP are mainly of macroscopic aspects. To shed light on the underlying neural mechanism of AP, we investigated the intracortical myeloarchitecture in musicians with and without AP using the quantitative mapping of the longitudinal relaxation rates with ultra-high-field magnetic resonance imaging at 7 T. We found greater intracortical myelination for AP musicians in the anterior region of the supratemporal plane, particularly the medial region of the right planum polare (PP). In the same region of the right PP, we also found a positive correlation with a behavioral index of AP performance. In addition, we found a positive correlation with a frequency discrimination threshold in the anterolateral Heschl's gyrus in the right hemisphere, demonstrating distinctive neural processes of absolute recognition and relative discrimination of pitch. Regarding possible effects of local myelination in the cortex and the known importance of the anterior superior temporal gyrus/sulcus for the identification of auditory objects, we argue that pitch chroma may be processed as an identifiable object property in AP musicians. Hum Brain Mapp 37:3486-3501, 2016. © 2016 Wiley Periodicals, Inc. PMID:27160707

  15. Dynamic multi-coil shimming of the human brain at 7 T

    NASA Astrophysics Data System (ADS)

    Juchem, Christoph; Nixon, Terence W.; McIntyre, Scott; Boer, Vincent O.; Rothman, Douglas L.; de Graaf, Robin A.

    2011-10-01

    High quality magnetic field homogenization of the human brain (i.e. shimming) for MR imaging and spectroscopy is a demanding task. The susceptibility differences between air and tissue are a longstanding problem as they induce complex field distortions in the prefrontal cortex and the temporal lobes. To date, the theoretical gains of high field MR have only been realized partially in the human brain due to limited magnetic field homogeneity. A novel shimming technique for the human brain is presented that is based on the combination of non-orthogonal basis fields from 48 individual, circular coils. Custom-built amplifier electronics enabled the dynamic application of the multi-coil shim fields in a slice-specific fashion. Dynamic multi-coil (DMC) shimming is shown to eliminate most of the magnetic field inhomogeneity apparent in the human brain at 7 T and provided improved performance compared to state-of-the-art dynamic shim updating with zero through third order spherical harmonic functions. The novel technique paves the way for high field MR applications of the human brain for which excellent magnetic field homogeneity is a prerequisite.

  16. Time-efficient fast spin echo imaging at 4.7 T with low refocusing angles.

    PubMed

    Lebel, R Marc; Wilman, Alan H

    2009-07-01

    An implementation of fast spin echo at 4.7 T designed for versatile and time-efficient T(2)-weighted imaging of the human brain is presented. Reduced refocusing angles (alpha < 180 degrees) were employed to overcome specific absorption rate (SAR) constraints and their effects on image quality assessed. Image intensity and tissue contrast variations from heterogeneous RF transmit fields and incidental magnetization transfer effects were investigated at reduced refocusing angles. We found that intraslice signal variations are minimized with refocusing angles near 180 degrees, but apparent gray/white matter contrast is independent of refocusing angle. Incidental magnetization transfer effects from multislice acquisitions were shown to attenuate white matter intensity by 25% and gray matter intensity by 15% at 180 degrees; less than 5% attenuation was seen in all tissues at flip angles below 60 degrees. We present multislice images acquired without excess delay time for SAR mitigation using a variety of protocols. Subsecond half Fourier acquisition single-shot turbo spin echo (HASTE) images were obtained with a novel variable refocusing angle echo train (20 degrees < alpha < 58 degrees) and high-resolution scans with a voxel volume of 0.18 mm(3) were acquired in 6.5 min with refocusing angles of 100 degrees.

  17. Intracortical myelination in musicians with absolute pitch: Quantitative morphometry using 7-T MRI.

    PubMed

    Kim, Seung-Goo; Knösche, Thomas R

    2016-10-01

    Absolute pitch (AP) is known as the ability to recognize and label the pitch chroma of a given tone without external reference. Known brain structures and functions related to AP are mainly of macroscopic aspects. To shed light on the underlying neural mechanism of AP, we investigated the intracortical myeloarchitecture in musicians with and without AP using the quantitative mapping of the longitudinal relaxation rates with ultra-high-field magnetic resonance imaging at 7 T. We found greater intracortical myelination for AP musicians in the anterior region of the supratemporal plane, particularly the medial region of the right planum polare (PP). In the same region of the right PP, we also found a positive correlation with a behavioral index of AP performance. In addition, we found a positive correlation with a frequency discrimination threshold in the anterolateral Heschl's gyrus in the right hemisphere, demonstrating distinctive neural processes of absolute recognition and relative discrimination of pitch. Regarding possible effects of local myelination in the cortex and the known importance of the anterior superior temporal gyrus/sulcus for the identification of auditory objects, we argue that pitch chroma may be processed as an identifiable object property in AP musicians. Hum Brain Mapp 37:3486-3501, 2016. © 2016 Wiley Periodicals, Inc.

  18. In vivo magnetic resonance imaging of spinal cord at 7T

    NASA Astrophysics Data System (ADS)

    Elshafiey, Ibrahim; Narayana, Ponnada A.

    2002-05-01

    In vivo diffusion tensor magnetic resonance imaging (DT-MRI) was implemented on a 7T magnetic resonance (MR) scanner to characterize the diffusion properties of normal and injured cords in rodents. An implanted RF coil was used for improving the signal to noise ratio. Complete diffusion tensor was determined by acquiring images with diffusion gradients applied along seven independent directions, each incremented in sixteen gradient steps. The diffusion gradient pulse width was chosen to be 12 ms, with maximum gradient amplitude of 200 mT/m resulting in a large b value of 6200 s/mm2. The attenuation of diffusion-weighted images with b was characterized by a biexponential decay, suggesting the presence of two components of water diffusion: fast diffusion and slow diffusion components. This is the first time that demonstrated the biexponential nature of diffusion in vivo spinal cord. The images were analyzed using a nonlinear regression with constrained minimization for calculating the trace and fractional anisotropy, two rotationally invariant diffusion indices. These two indices are useful for evaluating the pathology and integrity of fiber tracts. Both trace and fractional anisotropy are significantly affected by injury. This suggests that DT-MRI provides unique information about fiber tracts in injured cord.

  19. Progress on a Multichannel, Dual-Mixer Stability Analyzer

    NASA Technical Reports Server (NTRS)

    Kirk, Albert; Cole, Steven; Stevens, Gary; Tucker, Blake; Greenhall, Charles

    2005-01-01

    Several documents describe aspects of the continuing development of a multichannel, dual-mixer system for simultaneous characterization of the instabilities of multiple precise, low-noise oscillators. One of the oscillators would be deemed to be a reference oscillator, its frequency would be offset by an amount (100 Hz) much greater than the desired data rate, and each of the other oscillators would be compared with the frequency-offset signal by operation of a combination of hardware and software. A high-rate time-tag counter would collect zero-crossing times of the approximately equal 100-Hz beat notes. The system would effect a combination of interpolation and averaging to process the time tags into low-rate phase residuals at the desired grid times. Circuitry that has been developed since the cited prior article includes an eight-channel timer board to replace an obsolete commercial time-tag counter, plus a custom offset generator, cleanup loop, distribution amplifier, zero-crossing detector, and frequency divider.

  20. A multichannel time-domain brain oximeter for clinical studies

    NASA Astrophysics Data System (ADS)

    Contini, Davide; Spinelli, Lorenzo; Caffini, Matteo; Cubeddu, Rinaldo; Torricelli, Alessandro

    2009-07-01

    We developed and optimized a multichannel dual-wavelength time-domain brain oximeter for functional studies in the clinical environment. The system, mounted on a 19"-rack, is interfaced with instrumentation for monitoring physiological parameters and for stimuli presentation.

  1. Compressed sensing MRI with multichannel data using multicore processors.

    PubMed

    Chang, Ching-Hua; Ji, Jim

    2010-10-01

    Compressed sensing (CS) is a promising method to speed up MRI. Because most clinical MRI scanners are equipped with multichannel receive systems, integrating CS with multichannel systems may not only shorten the scan time but also provide improved image quality. However, significant computation time is required to perform CS reconstruction, whose complexity is scaled by the number of channels. In this article, we propose a reconstruction procedure that uses ubiquitously available multicore central processing unit to accelerate CS reconstruction from multiple channel data. The experimental results show that the reconstruction efficiency benefits significantly from parallelizing the CS reconstructions and pipelining multichannel data into multicore processors. In our experiments, an additional speedup factor of 1.6-2.0 was achieved using the proposed method on a quad-core central processing unit. The proposed method provides a straightforward way to accelerate CS reconstruction with multichannel data for parallel computation.

  2. Multichannel Kondo impurity dynamics in a Majorana device.

    PubMed

    Altland, A; Béri, B; Egger, R; Tsvelik, A M

    2014-08-15

    We study the multichannel Kondo impurity dynamics realized in a mesoscopic superconducting island connected to metallic leads. The effective "impurity spin" is nonlocally realized by Majorana bound states and strongly coupled to lead electrons by non-Fermi liquid correlations. We explore the spin dynamics and its observable ramifications near the low-temperature fixed point. The topological protection of the system raises the perspective to observe multichannel Kondo impurity dynamics in experimentally realistic environments.

  3. Packed multi-channels for parallel chromatographic separations in microchips.

    PubMed

    Nagy, Andrea; Gaspar, Attila

    2013-08-23

    Here we report on a simple method to fabricate microfluidic chip incorporating multi-channel systems packed by conventional chromatographic particles without the use of frits. The retaining effectivities of different bottlenecks created in the channels were studied. For the parallel multi-channel chromatographic separations several channel patterns were designed. The obtained multipackings were applied for parallel separations of dyes. The implementation of several chromatographic separation units in microscopic size makes possible faster and high throughput separations.

  4. Concurrent Visualization of Acoustic Radiation Force Displacement and Shear Wave Propagation with 7T MRI

    PubMed Central

    Liu, Yu; Fite, Brett Z.; Mahakian, Lisa M.; Johnson, Sarah M.; Larrat, Benoit; Dumont, Erik; Ferrara, Katherine W.

    2015-01-01

    Manual palpation is a common and very informative diagnostic tool based on estimation of changes in the stiffness of tissues that result from pathology. In the case of a small lesion or a lesion that is located deep within the body, it is difficult for changes in mechanical properties of tissue to be detected or evaluated via palpation. Furthermore, palpation is non-quantitative and cannot be used to localize the lesion. Magnetic Resonance-guided Focused Ultrasound (MRgFUS) can also be used to evaluate the properties of biological tissues non-invasively. In this study, an MRgFUS system combines high field (7T) MR and 3 MHz focused ultrasound to provide high resolution MR imaging and a small ultrasonic interrogation region (~0.5 x 0.5 x 2 mm), as compared with current clinical systems. MR-Acoustic Radiation Force Imaging (MR-ARFI) provides a reliable and efficient method for beam localization by detecting micron-scale displacements induced by ultrasound mechanical forces. The first aim of this study is to develop a sequence that can concurrently quantify acoustic radiation force displacements and image the resulting transient shear wave. Our motivation in combining these two measurements is to develop a technique that can rapidly provide both ARFI and shear wave velocity estimation data, making it suitable for use in interventional radiology. Secondly, we validate this sequence in vivo by estimating the displacement before and after high intensity focused ultrasound (HIFU) ablation, and we validate the shear wave velocity in vitro using tissue-mimicking gelatin and tofu phantoms. Such rapid acquisitions are especially useful in interventional radiology applications where minimizing scan time is highly desirable. PMID:26439259

  5. Activation of the dentate nucleus in a verb generation task: A 7T MRI study.

    PubMed

    Thürling, M; Küper, M; Stefanescu, R; Maderwald, S; Gizewski, E R; Ladd, M E; Timmann, D

    2011-08-01

    There is increasing evidence of a topographic organization within the human cerebellar cortex for motor and non-motor functions. Likewise, a subdivision of the dentate nucleus in a more dorsal and rostral motor domain and a more ventral and caudal non-motor domain has been proposed by Dum and Strick (2003) based on anatomical studies in monkey. In humans, however, very little is known about topographic organization within the dentate nucleus. Activation of the dentate nucleus in a verb generation task was examined in young and healthy subjects using ultra-highfield 7T functional magnetic resonance imaging (fMRI) with its increase in signal-to-noise ratio. Data of 17 subjects were included in statistical analysis. Subjects were asked to (i) read words (nouns) aloud presented on a screen, (ii) silently read the same nouns, (iii) silently generate the appropriate verbs to the same nouns and (iv) to silently repeat the names of the months. A block design was used. For image processing, a recently developed region of interest (ROI) driven normalization method of the dentate nuclei was applied. Activation related to motor speech (contrast aloud reading minus silent reading) was strongest in the rostral parts of the dentate nucleus. Dorsorostral activations were present bilaterally. Activation related to verb generation (contrast verb generation minus silent reading) was found in the ventrocaudal parts of the dentate nucleus on the right. The present findings are in good accordance with the anatomical data in monkeys and suggest that the human dentate nucleus can be subdivided into a rostral and more dorsal motor domain and a ventrocaudal non-motor domain. PMID:21640191

  6. Sodium inversion recovery MRI of the knee joint in vivo at 7T.

    PubMed

    Madelin, Guillaume; Lee, Jae-Seung; Inati, Souheil; Jerschow, Alexej; Regatte, Ravinder R

    2010-11-01

    The loss of proteoglycans (PG) in the articular cartilage is an early signature of osteoarthritis (OA). The ensuing changes in the fixed charge density in the cartilage can be directly linked to sodium concentration via charge balance. Sodium ions in the knee joint appear in two pools: in the synovial fluids or joint effusion where the ions are in free motion and bound within the cartilage tissue where the Na(+) ions have a restricted motion. The ions in these two compartments have therefore different T₁ and T₂ relaxation times. The purpose of this study is to demonstrate the feasibility of a fluid-suppressed 3D ultrashort TE radial sodium sequence by implementing an inversion recovery (IR) preparation of the magnetization at 7T. This method could allow a more accurate and more sensitive quantification of loss of PG in patients with OA. It is shown that adiabatic pulses offer significantly improved performance in terms of robustness to B₁ and B₀ inhomogeneities when compared to the hard pulse sequence. Power deposition considerations further pose a limit to the RF inversion power, and we demonstrate in simulations and experiments how a practical compromise can be struck between clean suppression of fluid signals and power deposition levels. Two IR sequences with different types of inversion pulses (a rectangular pulse and an adiabatic pulse) were tested on a liquid phantom, ex vivo on a human knee cadaver and then in vivo on five healthy volunteers, with a (Nyquist) resolution of ∼3.6 mm and a signal-to-noise ratio of ∼30 in cartilage without IR and ∼20 with IR. Due to specific absorption rate limitations, the total acquisition time was ∼17 min for the 3D radial sequence without inversion or with the rectangular IR, and 24:30 min for the adiabatic IR sequence. It is shown that the adiabatic IR sequence generates a more uniform fluid suppression over the whole sample than the rectangular IR sequence.

  7. Real-time decoding of brain responses to visuospatial attention using 7T fMRI.

    PubMed

    Andersson, Patrik; Pluim, Josien P W; Siero, Jeroen C W; Klein, Stefan; Viergever, Max A; Ramsey, Nick F

    2011-01-01

    Brain-Computer interface technologies mean to create new communication channels between our mind and our environment, independent of the motor system, by detecting and classifying self regulation of local brain activity. BCIs can provide patients with severe paralysis a means to communicate and to live more independent lives. There has been a growing interest in using invasive recordings for BCI to improve the signal quality. This also potentially gives access to new control strategies previously inaccessible by non-invasive methods. However, before surgery, the best implantation site needs to be determined. The blood-oxygen-level dependent signal changes measured with fMRI have been shown to agree well spatially with those found with invasive electrodes, and are the best option for pre-surgical localization. We show, using real-time fMRI at 7T, that eye movement-independent visuospatial attention can be used as a reliable control strategy for BCIs. At this field strength even subtle signal changes can be detected in single trials thanks to the high contrast-to-noise ratio. A group of healthy subjects were instructed to move their attention between three (two peripheral and one central) spatial target regions while keeping their gaze fixated at the center. The activated regions were first located and thereafter the subjects were given real-time feedback based on the activity in these regions. All subjects managed to regulate local brain areas without training, which suggests that visuospatial attention is a promising new target for intracranial BCI. ECoG data recorded from one epilepsy patient showed that local changes in gamma-power can be used to separate the three classes. PMID:22110702

  8. Multimodal 7T Imaging of Thalamic Nuclei for Preclinical Deep Brain Stimulation Applications

    PubMed Central

    Xiao, YiZi; Zitella, Laura M.; Duchin, Yuval; Teplitzky, Benjamin A.; Kastl, Daniel; Adriany, Gregor; Yacoub, Essa; Harel, Noam; Johnson, Matthew D.

    2016-01-01

    Precise neurosurgical targeting of electrode arrays within the brain is essential to the successful treatment of a range of brain disorders with deep brain stimulation (DBS) therapy. Here, we describe a set of computational tools to generate in vivo, subject-specific atlases of individual thalamic nuclei thus improving the ability to visualize thalamic targets for preclinical DBS applications on a subject-specific basis. A sequential nonlinear atlas warping technique and a Bayesian estimation technique for probabilistic crossing fiber tractography were applied to high field (7T) susceptibility-weighted and diffusion-weighted imaging, respectively, in seven rhesus macaques. Image contrast, including contrast within thalamus from the susceptibility-weighted images, informed the atlas warping process and guided the seed point placement for fiber tractography. The susceptibility-weighted imaging resulted in relative hyperintensity of the intralaminar nuclei and relative hypointensity in the medial dorsal nucleus, pulvinar, and the medial/ventral border of the ventral posterior nuclei, providing context to demarcate borders of the ventral nuclei of thalamus, which are often targeted for DBS applications. Additionally, ascending fiber tractography of the medial lemniscus, superior cerebellar peduncle, and pallidofugal pathways into thalamus provided structural demarcation of the ventral nuclei of thalamus. The thalamic substructure boundaries were validated through in vivo electrophysiological recordings and post-mortem blockface tissue sectioning. Together, these imaging tools for visualizing and segmenting thalamus have the potential to improve the neurosurgical targeting of DBS implants and enhance the selection of stimulation settings through more accurate computational models of DBS. PMID:27375422

  9. In vivo GABA T2 determination with J-refocused echo time extension at 7 T.

    PubMed

    Andreychenko, A; Klomp, D W J; de Graaf, R A; Luijten, P R; Boer, V O

    2013-11-01

    A method to measure the T2 relaxation time of GABA with spectral editing techniques is proposed. Spectral editing techniques can be used to unambiguously extract signals of low concentration J-coupled spins such as γ-aminobutyric acid (GABA) from overlapping resonances such as creatine and macromolecules. These sequences, however, generally have fixed and relatively long echo times. Therefore, for the absolute quantification of the edited spectrum, the T2 relaxation time must be taken into account. To measure the T2 relaxation time, the signal intensity has to be obtained at multiple echo times. However, on a coupled spin system such as GABA this is challenging, since the signal intensity of the target resonances is modulated not only by T2 decay but also by the J-coupling, which strongly influences the shapes and amplitudes of the edited signals, depending on the echo time. Here, we propose to refocus the J-modulation of the edited signal at different echo times by using chemical shift selective refocusing. In this way the echo time can be arbitrarily extended while preserving the shape of the edited signal. The method was applied in combination with the MEGA-sLASER editing technique to measure the in vivo T2 relaxation time of GABA (87 ± 11 ms, n = 10) and creatine (109 ± 8 ms, n = 10) at 7 T. The T1 relaxation time of these metabolites in a single subject was also determined (GABA, 1334 ± 158 ms; Cr, 1753 ± 12 ms). The T2 decay curve of coupled spin systems can be sampled in an arbitrary fashion without the need for signal shape correction. Furthermore, the method can be applied with any spectral editing technique. The shortest echo time of the method is limited by the echo time of the spectral editing technique.

  10. Multichannel mode conversion and multiplexing based on a single spatial light modulator for optical communication

    NASA Astrophysics Data System (ADS)

    Nie, Song; Yu, Song; Cai, Shanyong; Lan, Mingying; Gu, Wanyi

    2016-07-01

    A method is proposed to achieve multichannel mode conversion and multiplexing by dividing a single spatial light modulator into several blocks with the mode conversion pattern and blazed grating loaded on each block. The conversion patterns realize the precise excitation of higher order modes using combined amplitude and phase modulation. The blazed gratings bring together incident beams, so these beams can be coupled into few-mode fiber (FMF). In the experiment, four higher order modes are precisely excited and converge with a tilt angle. Through the simulation method, these beams can be coupled into FMF with small tilt angles (0.0344 deg for LP11 mode).

  11. Multichannel microwave interferometer with an antenna switching system for electron density measurement in a laboratory plasma experiment

    SciTech Connect

    Kawamori, Eiichirou; Lin, Yu-Hsiang; Mase, Atsushi; Nishida, Yasushi; Cheng, C. Z.

    2014-02-15

    This study presents a simple and powerful technique for multichannel measurements of the density profile in laboratory plasmas by microwave interferometry. This technique uses electromechanical microwave switches to temporally switch the connection between multiple receiver antennas and one phase-detection circuit. Using this method, the phase information detected at different positions is rearranged into a time series that can be acquired from a minimum number of data acquisition channels (e.g., two channels in the case of quadrature detection). Our successfully developed multichannel microwave interferometer that uses the antenna switching method was applied to measure the radial electron density profiles in a magnetized plasma experiment. The advantage of the proposed method is its compactness and scalability to multidimensional measurement systems at low cost.

  12. An eight-channel transmit/receive array of TE01 mode high permittivity ceramic resonators for human imaging at 7 T

    NASA Astrophysics Data System (ADS)

    Aussenhofer, S. A.; Webb, A. G.

    2014-06-01

    This study describes the design, construction and operation of a new type of transmit/receive array using ceramic resonators operating in a transverse electromagnetic (TE) mode. Single element function and performance at 298.1 MHz (7 T) are analyzed and compared to a lumped element design loop coil with comparable geometry. The results show that ceramic resonators working in the TE01δ mode configuration produce similar efficiency, defined as the transmit magnetic field (B1+) per square root of the specific absorption rate (SAR), to conventional surface coils. An array consisting of eight ceramic elements was then designed to operate in transmit/receive mode. This array was driven via power/phase splitters by two independent transmit channels and functional cardiac images were produced from a number of healthy volunteers.

  13. A CMOS Neural Interface for a Multichannel Vestibular Prosthesis

    PubMed Central

    Hageman, Kristin N.; Kalayjian, Zaven K.; Tejada, Francisco; Chiang, Bryce; Rahman, Mehdi A.; Fridman, Gene Y.; Dai, Chenkai; Pouliquen, Philippe O.; Georgiou, Julio; Della Santina, Charles C.; Andreou, Andreas G.

    2015-01-01

    We present a high-voltage CMOS neural-interface chip for a multichannel vestibular prosthesis (MVP) that measures head motion and modulates vestibular nerve activity to restore vision- and posture-stabilizing reflexes. This application specific integrated circuit neural interface (ASIC-NI) chip was designed to work with a commercially available microcontroller, which controls the ASIC-NI via a fast parallel interface to deliver biphasic stimulation pulses with 9-bit programmable current amplitude via 16 stimulation channels. The chip was fabricated in the ONSemi C5 0.5 micron, high-voltage CMOS process and can accommodate compliance voltages up to 12 V, stimulating vestibular nerve branches using biphasic current pulses up to 1.45 ± 0.06 mA with durations as short as 10 µs/phase. The ASIC-NI includes a dedicated digital-to-analog converter for each channel, enabling it to perform complex multipolar stimulation. The ASIC-NI replaces discrete components that cover nearly half of the 2nd generation MVP (MVP2) printed circuit board, reducing the MVP system size by 48% and power consumption by 17%. Physiological tests of the ASIC-based MVP system (MVP2A) in a rhesus monkey produced reflexive eye movement responses to prosthetic stimulation similar to those observed when using the MVP2. Sinusoidal modulation of stimulus pulse rate from 68–130 pulses per second at frequencies from 0.1 to 5 Hz elicited appropriately-directed slow phase eye velocities ranging in amplitude from 1.9–16.7°/s for the MVP2 and 2.0–14.2°/s for the MVP2A. The eye velocities evoked by MVP2 and MVP2A showed no significant difference (t-test, p = 0.034), suggesting that the MVP2A achieves performance at least as good as the larger MVP2. PMID:25974945

  14. 26 CFR 1.6049-7T - Market discount fraction reported with other financial information with respect to REMICs and...

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... financial information with respect to REMICs and collateralized debt obligations (temporary). 1.6049-7T... other financial information with respect to REMICs and collateralized debt obligations (temporary). For... financial information with respect to REMICs and other collateralized debt obligations, if the REMIC...

  15. Draft Genome Sequences of Agrobacterium nepotum Strain 39/7T and Agrobacterium sp. Strain KFB 330.

    PubMed

    Kuzmanović, Nemanja; Puławska, Joanna; Prokić, Anđelka; Ivanović, Milan; Zlatković, Nevena; Gašić, Katarina; Obradović, Aleksa

    2015-01-01

    Tumorigenic strains of Agrobacterium spp. are responsible for crown gall disease of numerous plant species. We present here draft genome sequences of nonpathogenic Agrobacterium nepotum strain 39/7(T) (CFBP 7436(T), LMG 26435(T)), isolated from crown gall tumor on Prunus cerasifera, and tumorigenic Agrobacterium sp. strain KFB 330 (CFBP 8308, LMG 28674), isolated from galls on raspberry. PMID:25908139

  16. 26 CFR 1.132-7T - Treatment of employer-operated eating facilities-1985 through 1988 (temporary).

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 26 Internal Revenue 2 2010-04-01 2010-04-01 false Treatment of employer-operated eating facilities... Excluded from Gross Income § 1.132-7T Treatment of employer-operated eating facilities—1985 through 1988...-operated eating facility for employees is excludable from gross income as a de minimis fringe only if—...

  17. 26 CFR 1.132-7T - Treatment of employer-operated eating facilities-1985 through 1988 (temporary).

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 26 Internal Revenue 2 2011-04-01 2011-04-01 false Treatment of employer-operated eating facilities... Excluded from Gross Income § 1.132-7T Treatment of employer-operated eating facilities—1985 through 1988...-operated eating facility for employees is excludable from gross income as a de minimis fringe only if—...

  18. 26 CFR 1.132-7T - Treatment of employer-operated eating facilities-1985 through 1988 (temporary).

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 26 Internal Revenue 2 2014-04-01 2014-04-01 false Treatment of employer-operated eating facilities... Excluded from Gross Income § 1.132-7T Treatment of employer-operated eating facilities—1985 through 1988...-operated eating facility for employees is excludable from gross income as a de minimis fringe only if—...

  19. 26 CFR 1.132-7T - Treatment of employer-operated eating facilities-1985 through 1988 (temporary).

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 26 Internal Revenue 2 2012-04-01 2012-04-01 false Treatment of employer-operated eating facilities... Excluded from Gross Income § 1.132-7T Treatment of employer-operated eating facilities—1985 through 1988...-operated eating facility for employees is excludable from gross income as a de minimis fringe only if—...

  20. 26 CFR 1.132-7T - Treatment of employer-operated eating facilities-1985 through 1988 (temporary).

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 26 Internal Revenue 2 2013-04-01 2013-04-01 false Treatment of employer-operated eating facilities... Excluded from Gross Income § 1.132-7T Treatment of employer-operated eating facilities—1985 through 1988...-operated eating facility for employees is excludable from gross income as a de minimis fringe only if—...

  1. Multichannel hierarchical image classification using multivariate copulas

    NASA Astrophysics Data System (ADS)

    Voisin, Aurélie; Krylov, Vladimir A.; Moser, Gabriele; Serpico, Sebastiano B.; Zerubia, Josiane

    2012-03-01

    This paper focuses on the classification of multichannel images. The proposed supervised Bayesian classification method applied to histological (medical) optical images and to remote sensing (optical and synthetic aperture radar) imagery consists of two steps. The first step introduces the joint statistical modeling of the coregistered input images. For each class and each input channel, the class-conditional marginal probability density functions are estimated by finite mixtures of well-chosen parametric families. For optical imagery, the normal distribution is a well-known model. For radar imagery, we have selected generalized gamma, log-normal, Nakagami and Weibull distributions. Next, the multivariate d-dimensional Clayton copula, where d can be interpreted as the number of input channels, is applied to estimate multivariate joint class-conditional statistics. As a second step, we plug the estimated joint probability density functions into a hierarchical Markovian model based on a quadtree structure. Multiscale features are extracted by discrete wavelet transforms, or by using input multiresolution data. To obtain the classification map, we integrate an exact estimator of the marginal posterior mode.

  2. Multi-Channel Capacitive Sensor Arrays

    PubMed Central

    Wang, Bingnan; Long, Jiang; Teo, Koon Hoo

    2016-01-01

    In this paper, multi-channel capacitive sensor arrays based on microstrip band-stop filters are studied. The sensor arrays can be used to detect the proximity of objects at different positions and directions. Each capacitive sensing structure in the array is connected to an inductive element to form resonance at different frequencies. The resonances are designed to be isolated in the frequency spectrum, such that the change in one channel does not affect resonances at other channels. The inductive element associated with each capacitive sensor can be surface-mounted inductors, integrated microstrip inductors or metamaterial-inspired structures. We show that by using metamaterial split-ring structures coupled to a microstrip line, the quality factor of each resonance can be greatly improved compared to conventional surface-mounted or microstrip meander inductors. With such a microstrip-coupled split-ring design, more sensing elements can be integrated in the same frequency spectrum, and the sensitivity can be greatly improved. PMID:26821023

  3. Development of multichannel MEG system at IGCAR

    NASA Astrophysics Data System (ADS)

    Mariyappa, N.; Parasakthi, C.; Gireesan, K.; Sengottuvel, S.; Patel, Rajesh; Janawadkar, M. P.; Radhakrishnan, T. S.; Sundar, C. S.

    2013-02-01

    We describe some of the challenging aspects in the indigenous development of the whole head multichannel magnetoencephalography (MEG) system at IGCAR, Kalpakkam. These are: i) fabrication and testing of a helmet shaped sensor array holder of a polymeric material experimentally tested to be compatible with liquid helium temperatures, ii) the design and fabrication of the PCB adapter modules, keeping in mind the inter-track cross talk considerations between the electrical leads used to provide connections from SQUID at liquid helium temperature (4.2K) to the electronics at room temperature (300K) and iii) use of high resistance manganin wires for the 86 channels (86×8 leads) essential to reduce the total heat leak which, however, inevitably causes an attenuation of the SQUID output signal due to voltage drop in the leads. We have presently populated 22 of the 86 channels, which include 6 reference channels to reject the common mode noise. The whole head MEG system to cover all the lobes of the brain will be progressively assembled when other three PCB adapter modules, presently under fabrication, become available. The MEG system will be used for a variety of basic and clinical studies including localization of epileptic foci during pre-surgical mapping in collaboration with neurologists.

  4. Multi-Channel Capacitive Sensor Arrays.

    PubMed

    Wang, Bingnan; Long, Jiang; Teo, Koon Hoo

    2016-01-01

    In this paper, multi-channel capacitive sensor arrays based on microstrip band-stop filters are studied. The sensor arrays can be used to detect the proximity of objects at different positions and directions. Each capacitive sensing structure in the array is connected to an inductive element to form resonance at different frequencies. The resonances are designed to be isolated in the frequency spectrum, such that the change in one channel does not affect resonances at other channels. The inductive element associated with each capacitive sensor can be surface-mounted inductors, integrated microstrip inductors or metamaterial-inspired structures. We show that by using metamaterial split-ring structures coupled to a microstrip line, the quality factor of each resonance can be greatly improved compared to conventional surface-mounted or microstrip meander inductors. With such a microstrip-coupled split-ring design, more sensing elements can be integrated in the same frequency spectrum, and the sensitivity can be greatly improved. PMID:26821023

  5. Time estimation with multichannel digital silicon photomultipliers.

    PubMed

    Venialgo, Esteban; Mandai, Shingo; Gong, Tim; Schaart, Dennis R; Charbon, Edoardo

    2015-03-21

    Accuracy in timemark estimation is crucial for time-of-flight positron emission tomography, in order to ensure high quality images after reconstruction. Since the introduction of multichannel digital silicon photomultipliers, it is possible to acquire several photoelectron timestamps for each individual gamma event. We study several timemark estimators based on multiple photoelectron timestamps by means of a comprehensive statistical model. In addition, we calculate the MSE of the estimators in comparison to the Cramér-Rao lower bound as a function of the system design parameters. We investigate the effect of skipping some of the photoelectron timestamps, which is a direct consequence of the limited number of time-to-digital converters and we propose a technique to compensate for this effect. In addition, we carry out an extensive analysis to evaluate the influence of dark counts on the detector timing performance. Moreover, we investigate the improvement of the timing performance that can be obtained with dark count filtering and we propose an appropriate filtering method based on measuring the time difference between sorted timestamps. Finally, we perform a full Monte Carlo simulation to compare different timemark estimators by exploring several system design parameters. It is demonstrated that a simple weighted-average estimator can achieve a comparable performance as the more complex maximum likelihood estimator.

  6. A novel multi-channel segmentation algorithm for X-ray microtomography data

    NASA Astrophysics Data System (ADS)

    Schlüter, Steffen

    2015-04-01

    X-ray microtomography has evolved into a standard technique for non-invasive imaging of inherent heterogeneity in rock and soil samples. As a prerequisite for quantitative image analysis the gray scale data has to be segmented into objects and background or multiple classes if more than two materials or phases are present in the image. In almost all cases a single gray value image serves as a basis for image segmentation. However, complimentary information could be provided from an additional image in order to help identify different classes with low contrast in the first image. This multi-channel segmentation is a standard method for RGB color images with three channels, and is also frequently used in other disciplines like remote sensing. This study explores the applicability of multi-channel segmentation for X-ray microtomography data. Instead of a single histogram, every phase evokes a cluster in the two- or multidimensional feature space. Fuzzy C-means clustering is used to assign combinations of gray values to certain phases. This can be combined with Markov random field segmentation to add neighborhood information to the class assignment. We demonstrate the novel segmentation method by two standard applications of X-ray µ-CT. First, we use dual-energy scans to improve the identification of two fluids in homogeneous sand. Second, we use morphology information as a second image channel to distinguish root channels from inter-aggregate pores in a silty loam sample.

  7. A comparison of distributional considerations with statistical analysis of resting state fMRI at 3T and 7T

    NASA Astrophysics Data System (ADS)

    Yang, Xue; Holmes, Martha J.; Newton, Allen T.; Morgan, Victoria L.; Landman, Bennett A.

    2012-02-01

    Ultra-high field 7T magnetic resonance imaging (MRI) offers potentially unprecedented spatial resolution of functional activity within the human brain through increased signal and contrast to noise ratios over traditional 1.5T and 3T MRI scanners. However, the effects physiological and imaging artifacts are also greatly increased. Traditional statistical parametric mapping theories based on distributional properties representative of data acquired at lower fields may be inadequate for new 7T data. Herein, we investigate the model fitting residuals based on two 7T and one 3T protocols. We find that model residuals are substantively more non-Gaussian at 7T relative to 3T. Imaging slices that passed through regions with peak inhomogeneity problems (e.g., mid-brain acquisitions for the 7T hippocampus) exhibited visually higher degrees of distortion along with spatially correlated and extreme values of kurtosis (a measure of non- Gaussianity). The impacts of artifacts have been previously addressed for 3T data by estimating the covariance matrix of the regression errors. We further extend the robust estimation approach for autoregressive models and evaluate the qualitative impacts of this technique relative to traditional inference. Clear differences in statistical significance are shown between inferences based on classical versus robust assumptions, which suggest that inferences based on Gaussian assumptions are subject to practical (as well as theoretical) concerns regarding their power and validity. Hence, modern statistical approaches, such as the robust autoregressive model posed herein, are appropriate and suitable for inference with ultra-high field functional magnetic resonance imaging.

  8. Sodium inversion recovery MRI of the knee joint in vivo at 7T

    NASA Astrophysics Data System (ADS)

    Madelin, Guillaume; Lee, Jae-Seung; Inati, Souheil; Jerschow, Alexej; Regatte, Ravinder R.

    2010-11-01

    The loss of proteoglycans (PG) in the articular cartilage is an early signature of osteoarthritis (OA). The ensuing changes in the fixed charge density in the cartilage can be directly linked to sodium concentration via charge balance. Sodium ions in the knee joint appear in two pools: in the synovial fluids or joint effusion where the ions are in free motion and bound within the cartilage tissue where the Na+ ions have a restricted motion. The ions in these two compartments have therefore different T1 and T2 relaxation times. The purpose of this study is to demonstrate the feasibility of a fluid-suppressed 3D ultrashort TE radial sodium sequence by implementing an inversion recovery (IR) preparation of the magnetization at 7T. This method could allow a more accurate and more sensitive quantification of loss of PG in patients with OA. It is shown that adiabatic pulses offer significantly improved performance in terms of robustness to B1 and B0 inhomogeneities when compared to the hard pulse sequence. Power deposition considerations further pose a limit to the RF inversion power, and we demonstrate in simulations and experiments how a practical compromise can be struck between clean suppression of fluid signals and power deposition levels. Two IR sequences with different types of inversion pulses (a rectangular pulse and an adiabatic pulse) were tested on a liquid phantom, ex vivo on a human knee cadaver and then in vivo on five healthy volunteers, with a (Nyquist) resolution of ∼3.6 mm and a signal-to-noise ratio of ∼30 in cartilage without IR and ∼20 with IR. Due to specific absorption rate limitations, the total acquisition time was ∼17 min for the 3D radial sequence without inversion or with the rectangular IR, and 24:30 min for the adiabatic IR sequence. It is shown that the adiabatic IR sequence generates a more uniform fluid suppression over the whole sample than the rectangular IR sequence.

  9. 7-T MRI in Cerebrovascular Diseases: Challenges to Overcome and Initial Results.

    PubMed

    Harteveld, Anita A; van der Kolk, Anja G; Zwanenburg, Jaco J M; Luijten, Peter R; Hendrikse, Jeroen

    2016-04-01

    . In this review, we will describe the key developments in the last decade of 7-T MRI of cerebrovascular diseases, subdivided for these 3 levels of assessment. PMID:27049246

  10. Compensation for z-directional non-uniformity of a monopole antenna at 7T MRI

    NASA Astrophysics Data System (ADS)

    Kim, Nambeom; Woo, Myung-Kyun; Kang, Chang-Ki

    2016-06-01

    The research was conducted to find ways to compensate for z-directional non-uniformity at a monopole antenna array (MA) coil by using a tilted optimized non-saturating excitation (TONE) pulse and to evaluate the feasibility of using the MA coil with the TONE pulse for anatomical and angiographic imaging. The sensitivity of a MA coil along the z-direction was measured by using an actual flip angle imaging pulse sequence with an oil phantom to evaluate the flip angle distributions of the MA coil for 7T magnetic resonance imaging (MRI). The effects on the z-directional uniformity were examined by using slow and fast TONE pulses, i.e., TONE SLOW and TONE FAST. T1- and T2* -weighted images of the human brain were also examined. The z-directional profiles of the TONE pulses were analyzed by using the average signal intensity throughout the brain. The effect of the TONE pulses on cerebral vessels was further examined by analyzing maximal intensity projections of T1-weighted images. With increasing the applied flip angles, the sensitivity slope slightly increased (0.044 per degree). For the MA coil, the TONE SLOWpulse yielded a compensated profile along the z-direction while the TONE HIGH pulse, which has a flat excitation profile along the z-direction, exhibited a tilted signal intensity toward the coil end, clearly indicating an intrinsic property of the MA coil. Similar to the phantom study, human brain images revealed z-directional symmetry around the peak value for the averaged signal intensity of the TONE SLOW pulse while the TONE HIGH pulse exhibited a tilted signal intensity toward the coil end. In vascular system imaging, the MA coil also clearly demonstrated a beneficial effect on the cerebral vessels, either with or without the TONE pulses. This study demonstrates that TONE pulses could compensate for the intrinsic z-directional non-uniformity of MA coils that exhibit strong uniformity in the x-y plane. Furthermore, tilted pulses, such as TONE pulses, were

  11. Brain intra- and extracellular sodium concentration in multiple sclerosis: a 7 T MRI study.

    PubMed

    Petracca, Maria; Vancea, Roxana O; Fleysher, Lazar; Jonkman, Laura E; Oesingmann, Niels; Inglese, Matilde

    2016-03-01

    Intra-axonal accumulation of sodium ions is one of the key mechanisms of delayed neuro-axonal degeneration that contributes to disability accrual in multiple sclerosis. In vivo sodium magnetic resonance imaging studies have demonstrated an increase of brain total sodium concentration in patients with multiple sclerosis, especially in patients with greater disability. However, total sodium concentration is a weighted average of intra- and extra-cellular sodium concentration whose changes reflect different tissue pathophysiological processes. The in vivo, non-invasive measurement of intracellular sodium concentration is quite challenging and the few applications in patients with neurological diseases are limited to case reports and qualitative assessments. In the present study we provide first evidence of the feasibility of triple quantum filtered (23)Na magnetic resonance imaging at 7 T, and provide in vivo quantification of global and regional brain intra- and extra-cellular sodium concentration in 19 relapsing-remitting multiple sclerosis patients and 17 heathy controls. Global grey matter and white matter total sodium concentration (respectively P < 0.05 and P < 0.01), and intracellular sodium concentration (both P < 0.001) were higher while grey matter and white matter intracellular sodium volume fraction (indirect measure of extracellular sodium concentration) were lower (respectively P = 0.62 and P < 0.001) in patients compared with healthy controls. At a brain regional level, clusters of increased total sodium concentration and intracellular sodium concentration and decreased intracellular sodium volume fraction were found in several cortical, subcortical and white matter regions when patients were compared with healthy controls (P < 0.05 family-wise error corrected for total sodium concentration, P < 0.05 uncorrected for multiple comparisons for intracellular sodium concentration and intracellular sodium volume fraction). Measures of total sodium

  12. Robust and high resolution hyperpolarized metabolic imaging of the rat heart at 7 t with 3d spectral‐spatial EPI

    PubMed Central

    Miller, Jack J.; Lau, Angus Z.; Teh, Irvin; Schneider, Jürgen E.; Kinchesh, Paul; Smart, Sean; Ball, Vicky; Sibson, Nicola R.

    2015-01-01

    Purpose Hyperpolarized metabolic imaging has the potential to revolutionize the diagnosis and management of diseases where metabolism is dysregulated, such as heart disease. We investigated the feasibility of imaging rodent myocardial metabolism at high resolution at 7 T. Methods We present here a fly‐back spectral‐spatial radiofrequency pulse that sidestepped maximum gradient strength requirements and enabled high resolution metabolic imaging of the rodent myocardium. A 3D echo‐planar imaging readout followed, with centric ordered z‐phase encoding. The cardiac gated sequence was used to image metabolism in rodents whose metabolic state had been manipulated by being fasted, fed, or fed and given the pyruvate dehydrogenase kinase inhibitor dichloroacetate. Results We imaged hyperpolarized metabolites with a spatial resolution of 2×2×3.8 mm3 and a temporal resolution of 1.8 s in the rat heart at 7 T. Significant differences in myocardial pyruvate dehydrogenase flux were observed between the three groups of animals, concomitant with the known biochemistry. Conclusion The proposed sequence was able to image in vivo metabolism with excellent spatial resolution in the rat heart. The field of view enabled the simultaneous multi‐organ acquisition of metabolic information from the rat, which is of great utility for preclinical research in cardiovascular disease. Magn Reson Med 000:000–000, 2015. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Magn Reson Med 75:1515–1524, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance. PMID:25991606

  13. Quantification of N-Acetyl Aspartyl Glutamate in Human Brain using Proton Magnetic Resonance Spectroscopy at 7 T

    NASA Astrophysics Data System (ADS)

    Elywa, M.

    2015-07-01

    The separation of N-acetyl aspartyl glutamate (NAAG) from N-acetyl aspartate (NAA) and other metabolites, such as glutamate, by in vivo proton magnetic resonance spectroscopy at 7 T is described. This method is based on the stimulated echo acquisition mode (STEAM), with short and long echo time (TE) and allows quantitative measurements of NAAG in the parietal and pregenual anterior cingulate cortex (pgACC) of human brain. Two basesets for the LCModel have been established using nuclear magnetic resonance simulator software (NMR-SIM). Six healthy volunteers (age 25-35 years) have been examined at 7 T. It has been established that NAAG can be separated and quantified in the parietal location and does not get quantified in the pgACC location when using a short echo time, TE = 20 ms. On the other hand, by using a long echo time, TE = 74 ms, NAAG can be quantified in pgACC structures.

  14. Is there any difference in Amide and NOE CEST effects between white and gray matter at 7 T?

    NASA Astrophysics Data System (ADS)

    Khlebnikov, Vitaliy; Siero, Jeroen C. W.; Wijnen, Jannie; Visser, Fredy; Luijten, Peter R.; Klomp, Dennis W. J.; Hoogduin, Hans

    2016-11-01

    Measurement of Chemical Exchange Saturation Transfer (CEST) is providing tissue physiology dependent contrast, e.g. by looking at Amide and NOE (Nuclear Overhauser Enhancement) effects. CEST is unique in providing quantitative metabolite information at high imaging resolution. However, direct comparison of Amide and NOE effects between different tissues may result in wrong conclusions on the metabolite concentration due to the additional contributors to the observed CEST contrast, such as water content (WC) and water T1 relaxation (T1w). For instance, there are multiple contradictory reports in the literature on Amide and NOE effects in white matter (WM) and gray matter (GM) at 7 T. This study shows that at 7 T, tissue water T1 relaxation is a stronger contributor to CEST contrasts than WC. After water T1 correction, there was no difference in Amide effects between WM and GM, whereas WM/GM contrast was enhanced for NOE effects.

  15. Nonadiabatic multichannel dynamics of a spin-orbit-coupled condensate

    NASA Astrophysics Data System (ADS)

    Xiong, Bo; Zheng, Jun-hui; Wang, Daw-wei

    2015-06-01

    We investigate the nonadiabatic dynamics of a driven spin-orbit-coupled Bose-Einstein condensate in both weak and strong driven force. It is shown that the standard Landau-Zener (LZ) tunneling fails in the regime of weak driven force and/or strong spin-orbital coupling, where the full nonadiabatic dynamics requires a new mechanism through multichannel effects. Beyond the semiclassical approach, our numerical and analytical results show an oscillating power-law decay in the quantum limit, different from the exponential decay in the semiclassical limit of the LZ effect. Furthermore, the condensate density profile is found to be dynamically fragmented by the multichannel effects and enhanced by interaction effects. Our work therefore provides a complete picture to understand the nonadiabatic dynamics of a spin-orbit coupled condensate, including various ranges of driven force and interaction effects through multichannel interference. The experimental indication of these nonadiabatic dynamics is also discussed.

  16. Wavelet-based compression of multichannel climate data

    NASA Astrophysics Data System (ADS)

    Sharifahmadian, Ershad; Choi, Yoonsuk; Latifi, Shahram; Dascalu, Sergiu; Harris, Frederick C.

    2014-05-01

    To simultaneously compress multichannel climate data, the Wavelet Subbands Arranging Technique (WSAT) is studied. The proposed technique is based on the wavelet transform, and has been designed to improve the transmission of voluminous climate data. The WSAT method significantly reduces the number of transmitted or stored bits in a bit stream, and preserves required quality. In the proposed technique, the arranged wavelet subbands of input channels provide more efficient compression for multichannel climate data due to building appropriate parent-offspring relations among wavelet coefficients. To test and evaluate the proposed technique, data from the Nevada climate change database is utilized. Based on results, the proposed technique can be an appropriate choice for the compression of multichannel climate data with significantly high compression ratio at low error.

  17. Restoration of color images by multichannel Kalman filtering

    NASA Technical Reports Server (NTRS)

    Galatsanos, Nikolas P.; Chin, Roland T.

    1991-01-01

    A Kalman filter for optimal restoration of multichannel images is presented. This filter is derived using a multichannel semicausal image model that includes between-channel degradation. Both stationary and nonstationary image models are developed. This filter is implemented in the Fourier domain and computation is reduced from O(Lambda3N3M4) to O(Lambda3N3M2) for an M x M N-channel image with degradation length Lambda. Color (red, green, and blue (RGB)) images are used as examples of multichannel images, and restoration in the RGB and YIQ domains is investigated. Simulations are presented in which the effectiveness of this filter is tested for different types of degradation and different image model estimates.

  18. Investigating neuronal activity by SPYCODE multi-channel data analyzer.

    PubMed

    Bologna, Luca Leonardo; Pasquale, Valentina; Garofalo, Matteo; Gandolfo, Mauro; Baljon, Pieter Laurens; Maccione, Alessandro; Martinoia, Sergio; Chiappalone, Michela

    2010-08-01

    Multi-channel acquisition from neuronal networks, either in vivo or in vitro, is becoming a standard in modern neuroscience in order to infer how cell assemblies communicate. In spite of the large diffusion of micro-electrode-array-based systems, researchers usually find it difficult to manage the huge quantity of data routinely recorded during the experimental sessions. In fact, many of the available open-source toolboxes still lack two fundamental requirements for treating multi-channel recordings: (i) a rich repertoire of algorithms for extracting information both at a single channel and at the whole network level; (ii) the capability of autonomously repeating the same set of computational operations to 'multiple' recording streams (also from different experiments) and without a manual intervention. The software package we are proposing, named SPYCODE, was mainly developed to respond to the above constraints and generally to offer the scientific community a 'smart' tool for multi-channel data processing. PMID:20554151

  19. A robust channel-calibration algorithm for multi-channel in azimuth HRWS SAR imaging based on local maximum-likelihood weighted minimum entropy.

    PubMed

    Zhang, Shuang-Xi; Xing, Meng-Dao; Xia, Xiang-Gen; Liu, Yan-Yang; Guo, Rui; Bao, Zheng

    2013-12-01

    High-resolution and wide-swath (HRWS) synthetic aperture radar (SAR) is an essential tool for modern remote sensing. To effectively deal with the contradiction problem between high-resolution and low pulse repetition frequency and obtain an HRWS SAR image, a multi-channel in azimuth SAR system has been adopted in the literature. However, the performance of the Doppler ambiguity suppression via digital beam forming processing suffers the losses from the channel mismatch. In this paper, a robust channel-calibration algorithm based on weighted minimum entropy is proposed for the multi-channel in azimuth HRWS SAR imaging. The proposed algorithm is implemented by a two-step process. 1) The timing uncertainty in each channel and most of the range-invariant channel mismatches in amplitude and phase have been corrected in the pre-processing of the coarse-compensation. 2) After the pre-processing, there is only residual range-dependent channel mismatch in phase. Then, the retrieval of the range-dependent channel mismatch in phase is achieved by a local maximum-likelihood weighted minimum entropy algorithm. The simulated multi-channel in azimuth HRWS SAR data experiment is adopted to evaluate the performance of the proposed algorithm. Then, some real measured airborne multi-channel in azimuth HRWS Scan-SAR data is used to demonstrate the effectiveness of the proposed approach. PMID:23893723

  20. In vivo 1D and 2D correlation MR spectroscopy of the soleus muscle at 7T

    NASA Astrophysics Data System (ADS)

    Ramadan, Saadallah; Ratai, Eva-Maria; Wald, Lawrence L.; Mountford, Carolyn E.

    2010-05-01

    AimThis study aims to (1) undertake and analyse 1D and 2D MR correlation spectroscopy from human soleus muscle in vivo at 7T, and (2) determine T1 and T2 relaxation time constants at 7T field strength due to their importance in sequence design and spectral quantitation. MethodSix healthy, male volunteers were consented and scanned on a 7T whole-body scanner (Siemens AG, Erlangen, Germany). Experiments were undertaken using a 28 cm diameter detunable birdcage coil for signal excitation and an 8.5 cm diameter surface coil for signal reception. The relaxation time constants, T1 and T2 were recorded using a STEAM sequence, using the 'progressive saturation' method for the T1 and multiple echo times for T2. The 2D L-Correlated SpectroscopY (L-COSY) method was employed with 64 increments (0.4 ms increment size) and eight averages per scan, with a total time of 17 min. ResultsT1 and T2 values for the metabolites of interest were determined. The L-COSY spectra obtained from the soleus muscle provided information on lipid content and chemical structure not available, in vivo, at lower field strengths. All molecular fragments within multiple lipid compartments were chemically shifted by 0.20-0.26 ppm at this field strength. 1D and 2D L-COSY spectra were assigned and proton connectivities were confirmed with the 2D method. ConclusionIn vivo 1D and 2D spectroscopic examination of muscle can be successfully recorded at 7T and is now available to assess lipid alterations as well as other metabolites present with disease. T1 and T2 values were also determined in soleus muscle of male healthy volunteers.

  1. Optical multichannel monitoring of skin blood pulsations for cardiovascular assessment

    NASA Astrophysics Data System (ADS)

    Spigulis, Janis; Erts, Renars; Ozols, Maris

    2004-07-01

    Time resolved detection and analysis of the skin back-scattered optical signals (reflection photoplethysmography or PPG) provide rich information on skin blood volume pulsations and can serve for cardiovascular assessment. The multichannel PPG concept has been developed and clinically verified in this work. Simultaneous data flow from several body locations allows to study the heartbeat pulse wave propagation in real time and to evaluate the vascular resistance. Portable two- and four-channel PPG monitoring devices and special software have been designed for real-time data acquisition and processing. The multi-channel devices were successfully applied for cardiovascular fitness tests and for early detection of arterial occlusions.

  2. Criteria of quality and methods of measurement in multichannel biotelemetry.

    PubMed

    Kaltschmidt, H

    1975-01-01

    In contrast with one-channel biotelemetry, multichannel biotelemetry systems permit the analysis of biological systems by means of cybernetics. Some simple examples are given. The basic concept of a multichannel system is described. The criteria of quality of which the nonevident ones are defined by detailing the test circuits are the following (input criteria): number of channels, bandwidth, voltage range, impedance, maximum voltage outside the signal band, stability of the power supply for transducers, factor of safety against multipath propagation, distance between transmitter and receiver, shock, vibration and temperature range, weight, volume and operating time. Output criteria: signal-to-noise ratio, linearity, crosstalk transfer function, different time lags.

  3. Multichannel MAC Layer In Mobile Ad—Hoc Network

    NASA Astrophysics Data System (ADS)

    Logesh, K.; Rao, Samba Siva

    2010-11-01

    This paper we presented the design objectives and technical challenges in Multichannel MAC protocols in Mobile Ad-hoc Network. In IEEE 802.11 a/b/g standards allow use of multiple channels, only a single channel is popularly used, due to the lack of efficient protocols that enable use of Multiple Channels. Even though complex environments in ad hoc networks require a combined control of physical (PHY) and medium access control (MAC) layers resources in order to optimize performance. And also we discuss the characteristics of cross-layer frame and give a multichannel MAC approach.

  4. Handling Deafness Problem of Scheduled Multi-Channel Polling MACs

    NASA Astrophysics Data System (ADS)

    Jiang, Fulong; Liu, Hao; Shi, Longxing

    Combining scheduled channel polling with channel diversity is a promising way for a MAC protocol to achieve high energy efficiency and performance under both light and heavy traffic conditions. However, the deafness problem may cancel out the benefit of channel diversity. In this paper, we first investigate the deafness problem of scheduled multi-channel polling MACs with experiments. Then we propose and evaluate two schemes to handle the deafness problem. Our experiment shows that deafness is a significant reason for performance degradation in scheduled multi-channel polling MACs. A proper scheme should be chosen depending on the traffic pattern and the design objective.

  5. Multichannel Analysis of Surface Waves and Dam Safety

    NASA Astrophysics Data System (ADS)

    Karastathis, V. K.

    2012-12-01

    Geophysical methodologies and particularly the Multichannel Analysis of Surface Waves (MASW) effectively proved their efficiency in the non-destructive testing of the dams, in the last decade, after many successful applications worldwide. The MASW method developed in the outset of this decade considerably improved the prospects and the validity of these geophysical applications. Since MASW and the other geophysical techniques do not require drilling they progressively increased their popularity significantly. The Multichannel Analysis of Surface Waves can be applied for the assessment of both earthen and concrete dams. Nevertheless, mostly cases of earthen dams can be found in the literature. The method can detect and map low shear wave velocity areas potentially associated with low cohesion zones due to differential settlement events in the core or increased seepage. The advantage of MASW is that it is not influenced by the water saturation of the interior of the dam contrary to other methods eg. p-wave tomography. Usually, a joint application of MASW with the p-wave techniques can be an optimal choice since the two methodologies can act complementary. An application of MASW on a three-dimensional structure, such as a dam, however, can actually be considered as a complicated problem since the effects of the lateral structural anomalies can strongly affect the results. For example, in an earthen dam the investigation of the core can be influenced by the presence of the shells. Therefore, the problem should be carefully examined by modeling all these the lateral anomalies with the aim to avoid a misinterpretation of the results. The effectiveness of MASW to the dam safety assessment is presented through two example applications, one at the Mornos Dam, an earthen dam responsible for the water supply of Athens, and a second one at the Marathon Dam which is a concrete dam also used for the water supply of Athens. In the case of Mornos Dam, MASW detected areas affected

  6. 26 CFR 1.103(n)-7T - Election to allocate State ceiling to certain facilities for local furnishing of electricity...

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 26 Internal Revenue 2 2013-04-01 2013-04-01 false Election to allocate State ceiling to certain facilities for local furnishing of electricity (temporary). 1.103(n)-7T Section 1.103(n)-7T Internal Revenue... certain facilities for local furnishing of electricity (temporary). (a) Election—(1) In general....

  7. 26 CFR 1.103(n)-7T - Election to allocate State ceiling to certain facilities for local furnishing of electricity...

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 26 Internal Revenue 2 2011-04-01 2011-04-01 false Election to allocate State ceiling to certain facilities for local furnishing of electricity (temporary). 1.103(n)-7T Section 1.103(n)-7T Internal Revenue... certain facilities for local furnishing of electricity (temporary). (a) Election—(1) In general....

  8. 26 CFR 1.103(n)-7T - Election to allocate State ceiling to certain facilities for local furnishing of electricity...

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 26 Internal Revenue 2 2014-04-01 2014-04-01 false Election to allocate State ceiling to certain facilities for local furnishing of electricity (temporary). 1.103(n)-7T Section 1.103(n)-7T Internal Revenue... certain facilities for local furnishing of electricity (temporary). (a) Election—(1) In general....

  9. 26 CFR 1.103(n)-7T - Election to allocate State ceiling to certain facilities for local furnishing of electricity...

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 26 Internal Revenue 2 2012-04-01 2012-04-01 false Election to allocate State ceiling to certain facilities for local furnishing of electricity (temporary). 1.103(n)-7T Section 1.103(n)-7T Internal Revenue... certain facilities for local furnishing of electricity (temporary). (a) Election—(1) In general....

  10. Development of data acquisition and analysis software for multichannel detectors

    SciTech Connect

    Chung, Y.

    1988-06-01

    This report describes the development of data acquisition and analysis software for Apple Macintosh computers, capable of controlling two multichannel detectors. With the help of outstanding graphics capabilities, easy-to-use user interface, and several other built-in convenience features, this application has enhanced the productivity and the efficiency of data analysis. 2 refs., 6 figs.

  11. Presentation of electromagnetic multichannel data: The signal space separation method

    NASA Astrophysics Data System (ADS)

    Taulu, Samu; Kajola, Matti

    2005-06-01

    Measurement of external magnetic fields provides information on electric current distribution inside an object. For example, in magnetoencephalography modern measurement devices sample the magnetic field produced by the brain in several hundred distinct locations around the head. The signal space separation (SSS) method creates a fundamental linear basis for all measurable multichannel signal vectors of magnetic origin. The SSS basis is based on the fact that the magnetic field can be expressed as a combination of two separate and rapidly converging expansions of harmonic functions with one expansion for signals arising from inside of the measurement volume of the sensor array and another for signals arising from outside of this volume. The separation is based on the different convergence volumes of the two expansions and on the fact that the sensors are located in a source current-free volume between the interesting and interfering sources. Individual terms of the expansions are shown to contain uncorrelated information of the underlying source distribution. SSS provides a stable decomposition of the measurement into a fundamental device-independent form when used with an accurately calibrated multichannel device. The external interference signals are elegantly suppressed by leaving the interference components out from the reconstruction based on the decomposition. Representation of multichannel data with the SSS basis is shown to provide a large variety of applications for improved analysis of multichannel data.

  12. Recent advances in Multi-Channel Algebraic Scattering

    SciTech Connect

    Karataglidis, S.; Fraser, P. R.; Amos, K.; Canton, L.; Pisent, G.; Svenne, J. P.; Knijff, D. van der

    2011-10-28

    For coupled-channel descriptions of low-energy nucleon-induced interactions involving nuclei with particle-unstable exited states, it is necessary to include the widths of the target states. How those widths may affect the elastic scattering cross sections is examined within the framework of the Multi-Channel Algebraic Scattering (MCAS) method.

  13. Microwave photonic integrator based on a multichannel fiber Bragg grating.

    PubMed

    Zhang, Jiejun; Yao, Jianping

    2016-01-15

    We propose and experimentally demonstrate a microwave photonic integrator based on a multichannel fiber Bragg grating (FBG) working in conjunction with a dispersion compensating fiber (DCF) to provide a step group delay response with no in-channel dispersion-related distortion. The multichannel FBG is designed based on the spectral Talbot effect, which provides a large group delay dispersion (GDD) within each channel. A step group delay response can then be achieved by cascading the multichannel FBG with a DCF having a GDD opposite the in-channel GDD. An optical comb, with each comb line located at the center of each channel of the FBG, is modulated by a microwave signal to be integrated. At the output of the DCF, multiple time-delayed replicas of the optical signal, with equal time delay spacing are obtained and are detected and summed at a photodetector (PD). The entire operation is equivalent to the integration of the input microwave signal. For a multichannel FBG with an in-channel GDD of 730 ps/nm and a DCF with an opposite GDD, an integrator with a bandwidth of 2.9 GHz and an integration time of 7 ns is demonstrated. PMID:26766692

  14. Multi-channel transimpedance measurement of a planar electromagnetic sensor array

    NASA Astrophysics Data System (ADS)

    Chen, Dixiang; Xie, Ruifang; Zhou, Weihong; Hu, Hengjiang; Pan, Mengchun

    2015-02-01

    Planar electromagnetic sensor arrays have advantages such as nice coherence, fast response speed and high sensitivity, which can be used for micro damage inspection of crucial parts in equipment, and the key point in improving the inspection performance is to achieve a precise measurement of multi-channel transimpedances (the inductive voltages divided by the exciting current of the sensor). The principle and characteristics of planar electromagnetic sensor arrays are introduced in this paper, and a digital lock-in impedance measurement algorithm was investigated, with which the interference and noise in inductive voltage signals can be restrained effectively and the amplitude and phase of the transimpedance can be obtained with good repeatability. An eight channel impedance measurement system was established based on a field programmable gate array and utilized to inspect the micro damage in metal materials, and the experimental data were analyzed. The experimental results show that the impedance measurement has excellent repeatability when the sensor array is placed in air, and the maximum measurement error of the complete transimpedance measurement system is lower than 10%. A micro crack with a size of 1 mm (length) × 0.1 mm (width) × 1 mm (depth) can be detected through the measurement of multi-channel transimpedance in the planar electromagnetic sensor array.

  15. Motion-Correction Enabled Ultra-High Resolution In-Vivo 7T-MRI of the Brain

    PubMed Central

    Federau, Christian

    2016-01-01

    Objectives To demonstrate the image quality that can be obtained for multiple contrasts using ultra-high resolution MRI (highest nominal resolution: 350 μm isotropic) at 7T using appropriate motion-correction. Materials and Methods An MRI-based fat-excitation motion navigator (which requires no additional hardware) was incorporated into T1-weighted (MP2RAGE, 350 μm nominal isotropic resolution, total scan time 124 mins over 2 sessions. The MP2RAGE also provides quantitative T1-maps), 3D-TSE (380 μm nominal isotropic resolution, total scan time 58 mins) and T2*-weighted protocols (3D-GRE, 380 μm nominal isotropic resolution, total scan time 42 mins) on a 7T MR system. Images from each contrast are presented from a single healthy adult male volunteer (34 years) for direct comparison. The subject provided written consent in accordance with the local review board. Results Images of various brain structures are revealed at unprecedented quality for in-vivo MRI. The presented images permit, for example, to delimit the internal structure of the basal ganglia and thalamus. The single digitationes of the hippocampus are visible, and the gyrus dentatus can be visualized. Intracortical contrast was also observed in the neocortex, including the stria of Gennari of the primary visual cortex. Conclusions Appropriate motion-correction allows MRI scans to be performed with extended scan times enabling exceptionally high resolution scans with high image quality, with the use of a 7T scanner allowing large brain coverage for 350–380 μm isotropic voxels with total scan times for each contrast ranging from 42 to 124 minutes. PMID:27159492

  16. GABA and Glutamate in Children with Primary Complex Motor Stereotypies: A 1H MRS Study at 7T

    PubMed Central

    Harris, A. D.; Singer, H. S.; Horska, A.; Kline, T.; Ryan, M.; Edden, R. A. E.; Mahone, E. Mark

    2015-01-01

    Background and Purpose Complex motor stereotypies (CMS) are rhythmic, repetitive, fixed, purposeful but purposeless movements that stop with distraction. They can occur in otherwise normal healthy children (primary stereotypies), as well in those with autism spectrum disorders (secondary stereotypies). The underlying neurobiological basis for these movements is unknown, but thought to involve cortical-striatal-thalamo-cortical pathways. In order to further clarify potential neurochemical alterations, GABA, glutamate (Glu), glutamine (Gln), N-acetyl aspartate (NAA) and choline (Cho) levels were measured in four frontostriatal regions, using 1H MRS at 7T. Materials and Methods A total of 18 children with primary CMS and 24 typically developing controls, ages 5-10 years completed MRS at 7T. Single voxel STEAM acquisitions from the anterior cingulate cortex (ACC), premotor cortex (PMC), dorsolateral prefrontal cortex (DLPFC) and striatum were obtained and metabolites were quantified with respect to creatine using LCModel. Results The 7T scan was well tolerated by all participants. Compared to controls, children with CMS had lower levels of GABA ACC (GABA/Cr, p=0.049; GABA/Glu: p=0.051) and striatum (GABA/Cr: p= 0.028; GABA/Glu: p=0.0037), but not the DLPFC or PMC. Glu, Gln, NAA, and Cho levels did not differ between groups in any of the aforementioned regions. Within the CMS group, reduced GABA/Cr in the ACC was significantly associated with greater severity of motor stereotypies (r=-0.59, p= 0.021). Conclusions These results suggest possible GABAergic dysfunction within corticostriatal pathways in children with primary CMS. PMID:26542237

  17. Investigation of the B1 field distribution and RF power deposition in a birdcage coil as functions of the number of coil legs at 4.7 T, 7.0 T, and 11.7 T

    NASA Astrophysics Data System (ADS)

    Seo, Jeung-Hoon; Han, Sang-Doc; Kim, Kyoung-Nam

    2015-06-01

    The proper design of birdcage (BC) coils plays a very important role in the acquisition of highresolution magnetic resonance imaging (MRI) of small animals such as rodents. In this context, we investigate multiple-leg (8-, 16-, 32-, 64-, and 128-leg) BC coils operating at ultra-high fields (UHF) of 7.0 T and 11.7 T and a high-field (HF) of 4.7 T for rodent magnetic resonance imaging (MRI). Primarily, Our study comparatively examines the parameters of the radiofrequency (RF) transmission (|B1 +|)-field, the magnetic flux (|B1|)-field, and RF power deposition (RF-PD) as functions of the number of BC-coil legs via finite-difference time-domain (FDTD) calculations under realistic loading conditions with a biological phantom. In particular, the specific ratio |E/B1 +| is defined for predicting RF-PD values in different coil structures. Our results indicate that the optimal number of legs of the BC coil can be chosen for different resonance frequencies of 200 MHz, 300 MHz, and 500 MHz and that this choice can be lead to superior |B1 +|-field intensity and |B1|-field homogeneity and decreased RF-PD. We believe that our approach to determining the optimal number of legs for a BC coil can contribute to rodent MR imaging.

  18. Correction of Gradient Nonlinearity Artifacts in Prospective Motion Correction for 7T MRI

    PubMed Central

    Yarach, U.; Luengviriya, C.; Danishad, K.A.; Stucht, D.; Godenschweger, F.; Schulze, P.; Speck, O.

    2014-01-01

    Purpose To demonstrate the effect of gradient nonlinearity and develop a method for correction of gradient non-linearity artifacts in prospective motion correction (Mo-Co). Methods Non-linear gradients can induce geometric distortions in MRI, leading to pixel shifts with errors of up to several millimeters, thereby interfering with precise localization of anatomical structures. Prospective Mo-Co has been extended by conventional gradient warp correction applied to individual phase encoding steps/groups during the reconstruction. The gradient-related displacements are approximated using Spherical Harmonic (SPH) functions. In addition, the combination of this method with a retrospective correction of the changes in the coil sensitivity profiles relative to the object (augmented SENSE) was evaluated in simulation and experimental data. Results Prospective Mo-Co under gradient fields and coils sensitivity inconsistencies results in residual blurring, spatial distortion, and coil sensitivity mismatch artifacts. These errors can be considerably mitigated by the proposed method. High image quality with very little remaining artifacts was achieved after a few iterations. The relative image errors decreased from 25.7% to below 17.3% after 10 iterations. Conclusion The combined correction of gradient non-linearity and sensitivity map variation leads to a pronounced reduction of residual motion artifacts in prospectively motion-corrected data. PMID:24798889

  19. Multichannel X-Band Dielectric-Resonator Oscillator

    NASA Technical Reports Server (NTRS)

    Mysoor, Narayan; Dennis, Matthew; Cook, Brian

    2006-01-01

    A multichannel dielectric-resonator oscillator (DRO), built as a prototype of a local oscillator for an X-band transmitter or receiver, is capable of being electrically tuned among and within 26 adjacent frequency channels, each 1.16 MHz wide, in a band ranging from 7,040 to 7,070 GHz. The tunability of this oscillator is what sets it apart from other DROs, making it possible to use mass-produced oscillator units of identical design in diverse X-band applications in which there are requirements to use different fixed frequencies or to switch among frequency channels. The oscillator (see figure) includes a custom-designed voltage-controlled-oscillator (VCO) monolithic microwave integrated circuit (MMIC), a dielectric resonator disk (puck), and two varactor-coupling circuits, all laid out on a 25-mil (0.635-mm)-thick alumina substrate having a length and width of 17.8 mm. The resonator disk has a diameter of 8.89 mm and a thickness of 4.01 mm. The oscillator is mounted in an 8.9-mm-deep cavity in a metal housing. The VCO MMIC incorporates a negative- resistance oscillator amplifier along with a buffer amplifier. The resonator disk is coupled to a microstrip transmission line connected to the negative-resistance port of the VCO MMIC. The two varactor-coupling circuits include microstrip lines, laid out orthogonally to each other, for coupling with the resonator disk. Each varactor microstrip line is DC-coupled to an external port via a microwave choke. One varactor is used for coarse tuning to select a channel; the other varactor is used (1) for fine tuning across the 1.16-MHz width of each channel and (2) as a feedback port for a phase-lock loop. The resonator disk is positioned to obtain (1) the most desirable bandwidth, (2) relatively tight coupling with the microstrip connected to the coarse-tuning varactor, and (3) relatively loose coupling with the microstrip connected to the fine-tuning varactor. Measurements of performance showed that the oscillator can be

  20. Multichannel seismic/oceanographic/biological monitoring of the oceans

    NASA Astrophysics Data System (ADS)

    Hello, Y.; Leymarie, E.; Ogé, A.; Poteau, A.; Argentino, J.; Sukhovich, A.; Claustre, H.; Nolet, G.

    2011-12-01

    Delays in seismic P wave are used to make scans or 3D images of the variations in seismic wave speed in the Earth's interior using the techniques of seismic tomography. Observations of such delays are ubiquitous on the continents but rare in oceanic regions. Free-drifting profiling floats that measure the temperature, salinity and current of the upper 2000 m of the ocean are used by physical oceanographers for continuous monitoring in the Argo program. Recently, seismologists developed the idea to use such floats in order to compensate for the lack of seismic delay observations, especially in the southern hemisphere. In project Globalseis, financed by a grant from the European Research Council (ERC), we have developed and tested a prototype of such a seismological sensor using an Apex float from Teledyne Webb Research, a Rafos hydrophone, and electronics developed in collaboration with Osean, a small engineering firm in France. `MERMAID', for `Mobile Earthquake Recorder in Marine Areas by Independent Divers' is approaching its final design and should become available off the shelf in 2012. In the meantime we initiated a collaboration between Globalseis and another ERC project, remOcean, for the acquisition of radiometric, bio-geochemical data and meteorological observations in addition to salinity and temperature (Bio-Argo program). In this collaboration of Geoazur and LOV (Laboratoire d'Océanologie de Villefranche sur mer), two laboratories located at the Observatory of Villefranche, we developed a multichannel acquisition hardware electronics called 'PAYLOAD' that allows commercial floats such as Apex (TWR) and Provor (NKE) to serve multiple observing missions simultaneously. Based on an algorithm using wavelet transforms PAYLOAD continuously analyzes acoustic signals to detect major seismic events and weather phenomena such rain, drizzle, open sea and ice during drift diving phase. The bio-geochemical and other parameters are recorded and analyzed during ascent

  1. Dynamic Tracking of Injected Mesenchymal Stem Cells after Myocardial Infarction in Rats: A Serial 7T MRI Study

    PubMed Central

    Chen, Xiuyu; Lu, Minjie; Ma, Ning; Yin, Gang; Cui, Chen

    2016-01-01

    Purpose. To track the fate of micron-sized particles of iron oxide (MPIO) labeled mesenchymal stem cells (MSCs) in vivo in a rat myocardial infarction model using 7T magnetic resonance imaging (MRI) scanner. Materials and Methods. Male MSCs (2 × 106/50 μL) dual-labeled with MPIO and CM-DiI were injected into the infarct periphery 7 days after myocardial infarction (MI). The control group received cell-free media injection. The temporal stem cell location, signal intensity, and cardiac function were dynamically assessed using a 7T MRI at 24 h before transplantation (baseline), 3 days, 2 weeks, and 4 weeks after transplantation, respectively. Results. MR hypointensities caused by MPIOs were observed on T2⁎-weighted images at all time points after MSCs injection. Cine-MRI showed that MSCs moderated progressive left ventricular remodeling. Double staining for iron and CD68 revealed that most of the iron-positive cells were CD68-positive macrophages. Real-time PCR for rat SRY gene showed the number of survival MSCs considerably decreased after transplantation. MSC-treated hearts had significantly increased capillary density in peri-infarct region and lower cardiomyocytes apoptosis and fibrosis formation. Conclusions. Iron particles are not a reliable marker for in vivo tracking the long-term fate of MSCs engraftment. Despite of poor cell retention, MSCs moderate left ventricular remodeling after MI. PMID:27656215

  2. After-pulsing, cross-talk, dark-count, and gain of MPPC under 7-T static magnetic field.

    PubMed

    Hirano, Yoshiyuki; Nishikido, Fumihiko; Kokuryo, Daisuke; Yamaya, Taiga

    2016-07-01

    Multi-pixel photon counters (MPPCs) have been used instead of photomultiplier tubes for positron emission tomography combined with magnetic resonance (PET-MR). However, the effects of the magnetic field (MF) on the intrinsic properties-gain, cross-talk, after-pulsing, and dark-count-have not been sufficiently investigated. Therefore, we measured these properties for two types of MPPCs-S10931-50P and S12572-50P-in a static 7-T MF. These properties were measured with a pulse-shape analysis using pulse data acquired by a digital oscilloscope in the presence of the MF (w/MF) and the absence of the MF (w/o MF) by changing the supplied over-voltages (from 0.95 to 2.1 V for S10931 and from 2.1 to 3.3 V for S12572). No significant differences between the w/MF and w/o MF cases were observed for either MPPC, suggesting that the gain, cross-talk, after-pulsing, and dark-count are insensitive to a 7-T MF. The present work shows that constant MPPC performance is expected under a strong MF and demonstrates positive results for PET-MR. PMID:27188511

  3. Dynamic Tracking of Injected Mesenchymal Stem Cells after Myocardial Infarction in Rats: A Serial 7T MRI Study.

    PubMed

    Chen, Xiuyu; Lu, Minjie; Ma, Ning; Yin, Gang; Cui, Chen; Zhao, Shihua

    2016-01-01

    Purpose. To track the fate of micron-sized particles of iron oxide (MPIO) labeled mesenchymal stem cells (MSCs) in vivo in a rat myocardial infarction model using 7T magnetic resonance imaging (MRI) scanner. Materials and Methods. Male MSCs (2 × 10(6)/50 μL) dual-labeled with MPIO and CM-DiI were injected into the infarct periphery 7 days after myocardial infarction (MI). The control group received cell-free media injection. The temporal stem cell location, signal intensity, and cardiac function were dynamically assessed using a 7T MRI at 24 h before transplantation (baseline), 3 days, 2 weeks, and 4 weeks after transplantation, respectively. Results. MR hypointensities caused by MPIOs were observed on T2(⁎)-weighted images at all time points after MSCs injection. Cine-MRI showed that MSCs moderated progressive left ventricular remodeling. Double staining for iron and CD68 revealed that most of the iron-positive cells were CD68-positive macrophages. Real-time PCR for rat SRY gene showed the number of survival MSCs considerably decreased after transplantation. MSC-treated hearts had significantly increased capillary density in peri-infarct region and lower cardiomyocytes apoptosis and fibrosis formation. Conclusions. Iron particles are not a reliable marker for in vivo tracking the long-term fate of MSCs engraftment. Despite of poor cell retention, MSCs moderate left ventricular remodeling after MI. PMID:27656215

  4. Dynamic Tracking of Injected Mesenchymal Stem Cells after Myocardial Infarction in Rats: A Serial 7T MRI Study

    PubMed Central

    Chen, Xiuyu; Lu, Minjie; Ma, Ning; Yin, Gang; Cui, Chen

    2016-01-01

    Purpose. To track the fate of micron-sized particles of iron oxide (MPIO) labeled mesenchymal stem cells (MSCs) in vivo in a rat myocardial infarction model using 7T magnetic resonance imaging (MRI) scanner. Materials and Methods. Male MSCs (2 × 106/50 μL) dual-labeled with MPIO and CM-DiI were injected into the infarct periphery 7 days after myocardial infarction (MI). The control group received cell-free media injection. The temporal stem cell location, signal intensity, and cardiac function were dynamically assessed using a 7T MRI at 24 h before transplantation (baseline), 3 days, 2 weeks, and 4 weeks after transplantation, respectively. Results. MR hypointensities caused by MPIOs were observed on T2⁎-weighted images at all time points after MSCs injection. Cine-MRI showed that MSCs moderated progressive left ventricular remodeling. Double staining for iron and CD68 revealed that most of the iron-positive cells were CD68-positive macrophages. Real-time PCR for rat SRY gene showed the number of survival MSCs considerably decreased after transplantation. MSC-treated hearts had significantly increased capillary density in peri-infarct region and lower cardiomyocytes apoptosis and fibrosis formation. Conclusions. Iron particles are not a reliable marker for in vivo tracking the long-term fate of MSCs engraftment. Despite of poor cell retention, MSCs moderate left ventricular remodeling after MI.

  5. A comparison and evaluation of reduced-FOV methods for multi-slice 7T human imaging.

    PubMed

    Wargo, Christopher J; Moore, Jay; Gore, John C

    2013-10-01

    Eight different reduced field-of-view (FOV) MRI techniques suitable for high field human imaging were implemented, optimized, and evaluated at 7T. These included selective Inner-Volume Imaging (IVI) based methods, and Outer-Volume Suppression (OVS) techniques, some of which were previously unexplored at ultra-high fields. Design considerations included use of selective composite excitation and adiabatic refocusing radio-frequency (RF) pulses to address B1 inhomogeneities, twice-refocused spin echo techniques, frequency-modulated pulses to sharply define suppressed regions, and pulse sequence designs to improve SNR in multi-slice scans. The different methods were quantitatively compared in phantoms and in vivo human brain images to provide measurements of relative signal to noise ratio (SNR), power deposition (specific absorption rate, SAR), suppression of signal, artifact strength and prevalence, and general image quality. Multi-slice signal losses in out-of-slice locations were simulated for IVI methods, and then measured experimentally across a range of slice numbers. Corrections for B1 nonuniformities demonstrated an improved SNR and a reduction in artifact power in the reduced-FOV, but produced an elevated SAR. Multi-slice sequences with reordering of pulses in traditional and twice-refocused IVI techniques demonstrated an improved SNR compared to conventional methods. The combined results provide a basis for use of reduced-FOV techniques for human imaging localized to a small FOV at 7T.

  6. The utility of multichannel local field potentials for brain-machine interfaces

    NASA Astrophysics Data System (ADS)

    Hwang, Eun Jung; Andersen, Richard A.

    2013-08-01

    Objective. Local field potentials (LFPs) that carry information about the subject's motor intention have the potential to serve as a complement or alternative to spike signals for brain-machine interfaces (BMIs). The goal of this study is to assess the utility of LFPs for BMIs by characterizing the largely unknown information coding properties of multichannel LFPs. Approach. Two monkeys were implanted, each with a 16-channel electrode array, in the parietal reach region where both LFPs and spikes are known to encode the subject's intended reach target. We examined how multichannel LFPs recorded during a reach task jointly carry reach target information, and compared the LFP performance to simultaneously recorded multichannel spikes. Main Results. LFPs yielded a higher number of channels that were informative about reach targets than spikes. Single channel LFPs provided more accurate target information than single channel spikes. However, LFPs showed significantly larger signal and noise correlations across channels than spikes. Reach target decoders performed worse when using multichannel LFPs than multichannel spikes. The underperformance of multichannel LFPs was mostly due to their larger noise correlation because noise de-correlated multichannel LFPs produced a decoding accuracy comparable to multichannel spikes. Despite the high noise correlation, decoders using LFPs in addition to spikes outperformed decoders using only spikes. Significance. These results demonstrate that multichannel LFPs could effectively complement spikes for BMI applications by yielding more informative channels. The utility of multichannel LFPs may be further augmented if their high noise correlation can be taken into account by decoders.

  7. Phase locking of a seven-channel continuous wave fibre laser system by a stochastic parallel gradient algorithm

    SciTech Connect

    Volkov, M V; Garanin, S G; Dolgopolov, Yu V; Kopalkin, A V; Kulikov, S M; Sinyavin, D N; Starikov, F A; Sukharev, S A; Tyutin, S V; Khokhlov, S V; Chaparin, D A

    2014-11-30

    A seven-channel fibre laser system operated by the master oscillator – multichannel power amplifier scheme is the phase locked using a stochastic parallel gradient algorithm. The phase modulators on lithium niobate crystals are controlled by a multichannel electronic unit with the microcontroller processing signals in real time. The dynamic phase locking of the laser system with the bandwidth of 14 kHz is demonstrated, the time of phasing is 3 – 4 ms. (fibre and integrated-optical structures)

  8. Magnetic ordering and non-Fermi-liquid behavior in the multichannel Kondo-lattice model

    NASA Astrophysics Data System (ADS)

    Irkhin, Valentin Yu.

    2016-05-01

    Scaling equations for the Kondo lattice in the paramagnetic and magnetically ordered phases are derived to next-leading order with account of spin dynamics. The results are applied to describe various mechanisms of the non-Fermi-liquid (NFL) behavior in the multichannel Kondo-lattice model where a fixed point occurs in the weak-coupling region. The corresponding temperature dependences of electronic and magnetic properties are discussed. The model describes naturally formation of a magnetic state with soft boson mode and small moment value. An important role of Van Hove singularities in the magnon spectral function is demonstrated. The results are rather sensitive to the type of magnetic ordering and space dimensionality, the conditions for NFL behavior being more favorable in the antiferromagnetic and 2D cases.

  9. Stabilizing soliton-based multichannel transmission with frequency dependent linear gain-loss

    NASA Astrophysics Data System (ADS)

    Chakraborty, Debananda; Peleg, Avner; Nguyen, Quan M.

    2016-07-01

    We report several major theoretical steps towards realizing stable long-distance multichannel soliton transmission in Kerr nonlinear waveguide loops. We find that transmission destabilization in a single waveguide is caused by resonant formation of radiative sidebands and investigate the possibility to increase transmission stability by optimization with respect to the Kerr nonlinearity coefficient γ. Moreover, we develop a general method for transmission stabilization, based on frequency dependent linear gain-loss in Kerr nonlinear waveguide couplers, and implement it in two-channel and three-channel transmission. We show that the introduction of frequency dependent loss leads to significant enhancement of transmission stability even for non-optimal γ values via decay of radiative sidebands, which takes place as a dynamic phase transition. For waveguide couplers with frequency dependent linear gain-loss, we observe stable oscillations of soliton amplitudes due to decay and regeneration of the radiative sidebands.

  10. Multichannel optical-fibre heterodyne interferometer for ultrasound detection of partial discharges in power transformers

    NASA Astrophysics Data System (ADS)

    Posada, J. E.; Garcia-Souto, J. A.; Rubio-Serrano, J.

    2013-09-01

    A multichannel interferometric system is proposed for the ultrasonic detection of partial discharges using intrinsic optical fibre sensors that may be immersed in oil. It is based on a heterodyne scheme which drives at least four sensor heads in order to localize the source of the acoustic emissions. Proper design of the sensing head improves its sensitivity through magnification and reaches a compact encapsulated probe able to be installed within power transformers. The optoelectronic implementation and the experimental tests are presented to optimize the resolution (4 channels—4 mrad). In addition, the results of ultrasound measurements at 150 kHz with an optical fibre sensor immersed in water in an acoustic test bench are shown, in which a resolution better than 10 Pa was obtained. Finally, the set-up for three-phase power transformers is demonstrated and characterized to detect and locate the source of acoustic emissions.

  11. The selection of field acquisition parameters for dispersion images from multichannel surface wave data

    USGS Publications Warehouse

    Zhang, S.X.; Chan, L.S.; Xia, J.

    2004-01-01

    The accuracy and resolution of surface wave dispersion results depend on the parameters used for acquiring data in the field. The optimized field parameters for acquiring multichannel analysis of surface wave (MASW) dispersion images can be determined if preliminary information on the phase velocity range and interface depth is available. In a case study on a fill slope in Hong Kong, the optimal acquisition parameters were first determined from a preliminary seismic survey prior to a MASW survey. Field tests using different sets of receiver distances and array lengths showed that the most consistent and useful dispersion images were obtained from the optimal acquisition parameters predicted. The inverted S-wave velocities from the dispersion curve obtained at the optimal offset distance range also agreed with those obtained by using direct refraction survey.

  12. A miniaturized ASIC-based multichannel scaler instrument

    SciTech Connect

    Ericson, M.N.; Turner, G.W.; McMillan, D.E.; Hoffheins, B.S.; Todd, R.A.; Hiller, J.M.

    1993-12-31

    A miniaturized multichannel scaler instrument has been developed to address size and operational constraints for data acquisition in a portable laser-induced luminescence system. The multichannel scaling (MCS) function is implemented as a programmable application specific integrated circuit (ASIC) with standard interfaces for control and data acquisition. The instrument is microcontroller-based with sufficient computing power for data manipulation and algorithmic processing. The unit includes electronics for laser control, and amplification and pulse height discrimination of PMT pulses. Modification of the instrument should allow use in nuclear, chemical, and spectroscopy related applications including Mossbauer experiments. Interfaces are incorporated allowing both computer-controlled and stand alone operation. Implementation of the MCS function as an ASIC and comparison with conventional implementations are discussed. Full characterization of the MCS is presented including differential non-linearity (DNL), bin dead time, and bandwidth measurements.

  13. Electronically scanned multichannel pressure transducer system for cryogenic environments

    NASA Technical Reports Server (NTRS)

    Chapman, John J.

    1990-01-01

    Research into the application of custom doped piezoresistive silicon pressure sensors has led to a multichannel pressure sensor design that will operate accurately and reliably at cryogenic temperatures. The thermal effects upon multichannel pressure sensors are mapped by thermal calibrations and are represented by sets of nth order coefficients specific to each sensor. The thermal offset and sensitivity variations are corrected by computer algorithms which scan the sensors, recall correction coefficients from thermally induced sensor variations, and apply these to correct the sensor's output measurement uncertainty to within 0.5 percent of full scale output for combined offset and sensitivity. A prototype sensor system has been fabricated, and performance test data are presented.

  14. The effect of a multichannel cochlear implant on phoneme perception.

    PubMed

    Välimaa, T T; Sorri, M J; Löppönen, H J

    2001-01-01

    This study was done to investigate the effects of a multichannel cochlear implant on phoneme perception in Finnish-speaking postlingually deafened adults. Phoneme recognition was studied with 100 prerecorded nonsense syllables (open-set) presented at 70 dB SPL, auditorily only, in a free-field situation. Ten subjects were tested before implantation both with and without a hearing aid (HA), and 3, 6 and 12 months after switching on the implant. Before implantation without a HA, the subjects did not recognize vowels, consonants or syllables. Four of the subjects used a HA before implantation, and the mean recognition scores of these subjects were 34% for vowels, 28% for consonants and 13% for syllables. One year after switching on the implant, the mean recognition scores were 77% for vowels, 66% for consonants and 46% for syllables. According to phonological analysis vowels appear to be easier to perceive than consonants during the first stage after multichannel cochlear implantation.

  15. Multi-channel atomic magnetometer for magnetoencephalography: a configuration study.

    PubMed

    Kim, Kiwoong; Begus, Samo; Xia, Hui; Lee, Seung-Kyun; Jazbinsek, Vojko; Trontelj, Zvonko; Romalis, Michael V

    2014-04-01

    Atomic magnetometers are emerging as an alternative to SQUID magnetometers for detection of biological magnetic fields. They have been used to measure both the magnetocardiography (MCG) and magnetoencephalography (MEG) signals. One of the virtues of the atomic magnetometers is their ability to operate as a multi-channel detector while using many common elements. Here we study two configurations of such a multi-channel atomic magnetometer optimized for MEG detection. We describe measurements of auditory evoked fields (AEF) from a human brain as well as localization of dipolar phantoms and auditory evoked fields. A clear N100m peak in AEF was observed with a signal-to-noise ratio of higher than 10 after averaging of 250 stimuli. Currently the intrinsic magnetic noise level is 4fTHz(-1/2) at 10Hz. We compare the performance of the two systems in regards to current source localization and discuss future development of atomic MEG systems.

  16. Design and test of a double-nuclear RF coil for 1H MRI and 13C MRSI at 7 T

    NASA Astrophysics Data System (ADS)

    Rutledge, Omar; Kwak, Tiffany; Cao, Peng; Zhang, Xiaoliang

    2016-06-01

    RF coil operation at the ultrahigh field of 7 T is fraught with technical challenges that limit the advancement of novel human in vivo applications at 7 T. In this work, a hybrid technique combining a microstrip transmission line and a lumped-element L-C loop coil to form a double-nuclear RF coil for proton magnetic resonance imaging and carbon magnetic resonance spectroscopy at 7 T was proposed and investigated. Network analysis revealed a high Q-factor and excellent decoupling between the coils. Proton images and localized carbon spectra were acquired with high sensitivity. The successful testing of this novel double-nuclear coil demonstrates the feasibility of this hybrid design for double-nuclear MR imaging and spectroscopy studies at the ultrahigh field of 7 T.

  17. Transumbilical Retrieval of Surgical Specimens Through a Multichannel Port

    PubMed Central

    Ju, Da Hye; Lee, Sang Soo; Sohn, Woo Seok

    2014-01-01

    Background: Laparoscopic surgery is often used to excise adnexal masses; however, the retrieval of specimens such as large cystic masses through conventional 5- or 10-mm ports is difficult and time-consuming. We compared outcomes between conventional laparoscopic surgery for adnexal masses and transumbilical specimen retrieval through a multichannel port during single- or 2-port laparoscopy. Methods: A total of 341 patients who underwent laparoscopic surgery for adnexal masses from November 2006 to December 2010 were included. The patients were divided into 2 groups: group I consisted of 249 patients who underwent conventional laparoscopy, and group II consisted of 92 patients who underwent single- or 2-port laparoscopy using a multichannel port. The clinical characteristics and operative outcomes of the 2 groups were compared. Results: The mean operation time was 51.8 ± 21.5 minutes in group I and 57.2 ± 23.9 minutes in group II. The mean specimen retrieval time was longer in group I (2.9 ± 4.0 minutes) than in group II (2.2 ± 1.8 minutes). Endoscopic bag rupture during specimen retrieval occurred in 11 patients in group I and in no patients in group II. Conclusions: The transumbilical retrieval of surgical specimens through a multichannel port with a wound retractor was safe and did not result in leakage of the cystic contents. This technique reduced the specimen retrieval time, especially for large masses. However, the mean operation time was not shortened with this procedure, because of the learning period and the time required to prepare the umbilical multichannel port. PMID:25408603

  18. Construction of a CCD multichannel fiberoptic spectrometer and its application

    SciTech Connect

    Y. Qiu; X.Z. Qu; Q. Song

    1996-12-31

    A multichannel spectrometer was constructed with a linear CCD and a fiber-optic probe, which can perform in situ and quick spectrum measurement. Being linked to a PC computer, this spectrometer is especially suitable for dynamical process monitoring. The application of this instrumentation in the research of peroxyoxalate chemiluminescence has revealed the wavelength shift of the light emitting spectrum of rhodamine 6G during the chemiluminescent reaction. 8 refs., 7 figs.

  19. A multichannel EEG telemetry system utilizing a PCM subcarrier

    NASA Technical Reports Server (NTRS)

    Fryer, T. B.

    1974-01-01

    A multichannel personal-type telemetry system is described that utilizes PCM encoding for the most effective range with minimum RF bandwidth and noise interference. Recent IC developments (COS MOS) make it possible to implement a sophisticated encoding system (PCM) within the low power and size constraints necessary for a personal biotelemetry system. This system includes low-level high-impedance preamplifiers to make the system suitable for EEG recording.

  20. [Programmable multichannel electrophysiological stimulator based on MCU and CPLD platform].

    PubMed

    Zheng, Yi; Wu, Xiao-Mei; Fang, Zu-Xiang

    2008-01-01

    According to the instruction of the operator, the designed programmable multichannel stimulator will deliver stimuli with an assigned amplitude and a proper width to the electrode-array in various modes. Each stimulation time is controlled by the internal timer of the MCU, while the stimulated electrodes' spatial parameter is controlled by the CPLD. Having abandoned conventional isolation using the transformer, we have adapted optical coupling and stable float ground connection to achieve the safety standard required by physiological measurements.

  1. A method for multichannel dosimetry with EBT3 radiochromic films

    SciTech Connect

    Pérez Azorín, Jose Fernando

    2014-06-15

    Purpose: An improved method for multichannel dosimetry is presented. This method explicitly takes into account the information provided by the unexposed image of the film. Methods: The method calculates the dose by applying a couple of perturbations to the scanned dose, one dependent and the other independent on the color channel. The method has been compared with previous multichannel and two single channel methods (red and green) against measurements using two different tests: first, five percentage depth dose profiles covering a wide range of doses; second, the dose map perpendicular to the beam axis for a 15 × 15cm{sup 2} square field. Finally, the results of 30 IMRT quality assurances tests are presented. All tests have been evaluated using the gamma analysis. Results: The coefficient of variation was found to be similar for all methods in a wide range of doses. The results of the proposed method are more in agreement with the experimental measurements and with the treatment planning system. Furthermore, the differences in the mean gamma pass rates are statistically significant. Conclusions: The improved multichannel dosimetric method is able to remove many of the common disturbances usually present in radiochromic films and improves the gamma analysis results compared with the other three methods.

  2. Ultracold Long-Range Rydberg Molecules with Complex Multichannel Spectra

    NASA Astrophysics Data System (ADS)

    Eiles, Matthew; Greene, Chris

    2016-05-01

    A generalized class of exotic long-range Rydberg molecules consisting of a multichannel Rydberg atom bound to a distant ground state atom by the Rydberg electron is predicted. These molecules are characterized by the rich physics provided by the strongly perturbed multichannel Rydberg spectra of divalent atoms, in contrast to the regular Rydberg series of the alkali atoms used to form Rydberg molecules to date. These multichannel Rydberg molecules exhibit favorable properties for laser excitation, because states exist where the quantum defect varies strongly with the principal quantum number n. In particular, the nd Rydberg state of calcium becomes nearly degenerate with states of high orbital angular momentum over the range 17 < n < 22 , promoting its admixture into the high l deeply bound ``trilobite'' molecule states and thereby circumventing the usual difficulty posed by electric dipole selection rules. Further novel molecular states are predicted to occur in the low- J states of silicon, which are strongly perturbed due to channel interactions between Rydberg series leading to the spin-orbit split ionization thresholds. These interactions manifest themselves in potential curves exhibiting two distinct length scales, providing novel opportunities for quantum manipulation. Supported in part by the National Science Foundation under Grant No. PHY-1306905.

  3. Raman and multichannel Raman spectroscopy of biological systems

    NASA Astrophysics Data System (ADS)

    Bertoluzza, Alessandro; Caramazza, R.; Fagnano, C.

    1991-05-01

    Raman and multichannel Raman spectroscopy are molecular techniques able to monitor the bulk and surface structure of a biomaterial, in a non destructive and non invasive way, giving therefore useful information on physical and chemical aspects of biocompatibility. The same techniques can also be adequately used for the characterization of the biomaterial-host tissue interface, hence providing structural information on the biochemical aspect of biocompatibility. Moreover, multichannel Raman spectroscopy can also determine "in vivo" and "in situ" the bulk and surface structure of a biomaterial and the molecular interactions between biomaterials and tissues. Useful information at a molecular level on the biomaterial-tissue system can so be deduced. In particular, the application of traditional Paman spectroscopy to bioactive glasses (glasses derived from Hench's bioglass and meta and oligophosphates of calcium by themselves and with the addition of sodium and aluminium) useful in orthopedics and the application to hydrophobic (PMMA) and hydrophilic (PHEMA and PVP) organic polymers useful in ophthalmology are shown. Instead the applications of multichannel Paman spectroscopy are elucidated in the case of intraocular lenses (lOLs) based on PMMA and contact lenses (CLs) based on hydrophi I ic polymers.

  4. Sub-millimeter T2 weighted fMRI at 7 T: comparison of 3D-GRASE and 2D SE-EPI

    PubMed Central

    Kemper, Valentin G.; De Martino, Federico; Vu, An T.; Poser, Benedikt A.; Feinberg, David A.; Goebel, Rainer; Yacoub, Essa

    2015-01-01

    Functional magnetic resonance imaging (fMRI) allows studying human brain function non-invasively up to the spatial resolution of cortical columns and layers. Most fMRI acquisitions rely on the blood oxygenation level dependent (BOLD) contrast employing T*2 weighted 2D multi-slice echo-planar imaging (EPI). At ultra-high magnetic field (i.e., 7 T and above), it has been shown experimentally and by simulation, that T2 weighted acquisitions yield a signal that is spatially more specific to the site of neuronal activity at the cost of functional sensitivity. This study compared two T2 weighted imaging sequences, inner-volume 3D Gradient-and-Spin-Echo (3D-GRASE) and 2D Spin-Echo EPI (SE-EPI), with evaluation of their imaging point-spread function (PSF), functional specificity, and functional sensitivity at sub-millimeter resolution. Simulations and measurements of the imaging PSF revealed that the strongest anisotropic blurring in 3D-GRASE (along the second phase-encoding direction) was about 60% higher than the strongest anisotropic blurring in 2D SE-EPI (along the phase-encoding direction). In a visual paradigm, the BOLD sensitivity of 3D-GRASE was found to be superior due to its higher temporal signal-to-noise ratio (tSNR). High resolution cortical depth profiles suggested that the contrast mechanisms are similar between the two sequences, however, 2D SE-EPI had a higher surface bias owing to the higher T*2 contribution of the longer in-plane EPI echo-train for full field of view compared to the reduced field of view of zoomed 3D-GRASE. PMID:25999810

  5. An alternate algorithm for correction of the scanning multichannel microwave radiometer polarization radiances using Nimbus-7 observed data

    NASA Technical Reports Server (NTRS)

    Gloersen, P.; Cavalieri, D. J.; Soule, H. V.

    1980-01-01

    The manner in which Nimbus-7 scanning multichannel microwave radiometer (SMMR) scan radiance data was used to determine its operational characteristics is described. The predicted SMMR scan radiance was found to be in disagreement at all wavelengths with a large area of average measured ocean radiances. A modified model incorporating a different phase shift for each of the SMMR horizontal and vertical polarization channels was developed and found to provide good data correlation. Additional study is required to determine the validity and accuracy of this model.

  6. Multichannel, time-resolved picosecond laser ultrasound imaging and spectroscopy with custom complementary metal-oxide-semiconductor detector

    SciTech Connect

    Smith, Richard J.; Light, Roger A.; Johnston, Nicholas S.; Pitter, Mark C.; Somekh, Mike G.; Sharples, Steve D.

    2010-02-15

    This paper presents a multichannel, time-resolved picosecond laser ultrasound system that uses a custom complementary metal-oxide-semiconductor linear array detector. This novel sensor allows parallel phase-sensitive detection of very low contrast modulated signals with performance in each channel comparable to that of a discrete photodiode and a lock-in amplifier. Application of the instrument is demonstrated by parallelizing spatial measurements to produce two-dimensional thickness maps on a layered sample, and spectroscopic parallelization is demonstrated by presenting the measured Brillouin oscillations from a gallium arsenide wafer. This paper demonstrates the significant advantages of our approach to pump probe systems, especially picosecond ultrasonics.

  7. A compact multichannel spectrometer for Thomson scattering.

    PubMed

    Schoenbeck, N L; Schlossberg, D J; Dowd, A S; Fonck, R J; Winz, G R

    2012-10-01

    The availability of high-efficiency volume phase holographic (VPH) gratings and intensified CCD (ICCD) cameras have motivated a simplified, compact spectrometer for Thomson scattering detection. Measurements of T(e) < 100 eV are achieved by a 2971 l∕mm VPH grating and measurements T(e) > 100 eV by a 2072 l∕mm VPH grating. The spectrometer uses a fast-gated (~2 ns) ICCD camera for detection. A Gen III image intensifier provides ~45% quantum efficiency in the visible region. The total read noise of the image is reduced by on-chip binning of the CCD to match the 8 spatial channels and the 10 spectral bins on the camera. Three spectrometers provide a minimum of 12 spatial channels and 12 channels for background subtraction. PMID:23126988

  8. A compact multichannel spectrometer for Thomson scattering

    SciTech Connect

    Schoenbeck, N. L.; Schlossberg, D. J.; Dowd, A. S.; Fonck, R. J.; Winz, G. R.

    2012-10-15

    The availability of high-efficiency volume phase holographic (VPH) gratings and intensified CCD (ICCD) cameras have motivated a simplified, compact spectrometer for Thomson scattering detection. Measurements of T{sub e} < 100 eV are achieved by a 2971 l/mm VPH grating and measurements T{sub e} > 100 eV by a 2072 l/mm VPH grating. The spectrometer uses a fast-gated ({approx}2 ns) ICCD camera for detection. A Gen III image intensifier provides {approx}45% quantum efficiency in the visible region. The total read noise of the image is reduced by on-chip binning of the CCD to match the 8 spatial channels and the 10 spectral bins on the camera. Three spectrometers provide a minimum of 12 spatial channels and 12 channels for background subtraction.

  9. A compact multichannel spectrometer for Thomson scatteringa)

    NASA Astrophysics Data System (ADS)

    Schoenbeck, N. L.; Schlossberg, D. J.; Dowd, A. S.; Fonck, R. J.; Winz, G. R.

    2012-10-01

    The availability of high-efficiency volume phase holographic (VPH) gratings and intensified CCD (ICCD) cameras have motivated a simplified, compact spectrometer for Thomson scattering detection. Measurements of Te < 100 eV are achieved by a 2971 l/mm VPH grating and measurements Te > 100 eV by a 2072 l/mm VPH grating. The spectrometer uses a fast-gated (˜2 ns) ICCD camera for detection. A Gen III image intensifier provides ˜45% quantum efficiency in the visible region. The total read noise of the image is reduced by on-chip binning of the CCD to match the 8 spatial channels and the 10 spectral bins on the camera. Three spectrometers provide a minimum of 12 spatial channels and 12 channels for background subtraction.

  10. Multichannel Ultrasonic Data Communications in Air Using Range-Dependent Modulation Schemes.

    PubMed

    Jiang, Wentao; Wright, William M D

    2016-01-01

    There are several well-developed technologies of wireless communication such as radio frequency (RF) and infrared (IR), but ultrasonic methods can be a good alternative in some situations. A multichannel airborne ultrasonic data communication system is described in this paper. ON-OFF keying (OOK) and binary phase-shift keying (BPSK) modulation schemes were implemented successfully in the system by using a pair of commercially available capacitive ultrasonic transducers in a relatively low multipath indoor laboratory environment. Six channels were used from 50 to 110 kHz with a channel spacing of 12 kHz, allowing multiple 8-bit data packets to be transmitted simultaneously. The system data transfer rate achieved was up to 60 kb/s and ultrasonic wireless synchronization was implemented instead of using a hard-wired link. A model developed in the work could accurately predict ultrasonic signals through the air channels. Signal root mean square (rms) values and system bit error rates (BERs) were analyzed over different distances. Error-free decoding was achieved over ranges up to 5 m using a multichannel OOK modulation scheme. To obtain the highest data transfer rate and the longest error-free transmission distance, a range-dependent multichannel scheme with variable data rates, channel frequencies, and different modulation schemes, was also studied in the work. Within 2 m, error-free transmission was achieved using a five-channel OOK with a data rate of 63 kb/s. Between 2 and 5 m, six-channel OOK with 60 kb/s data transfer rate was error free. Beyond 5 m, the error-free transmission range could be extended up to 10 m using three-channel BPSK with a reduced data rate of 30 kb/s. The situation when two transducers were misaligned using three-channel OOK and BPSK schemes was also investigated in the work. It was concluded that error-free transmission could still be achieved with a lateral displacement of less than 7% and oblique angles of less than 7°, and three

  11. Simultaneous source separation using a new multichannel matching pursuit method with directional features

    NASA Astrophysics Data System (ADS)

    Cao, J.; Gu, H.

    2015-12-01

    Simultaneous source technology allows us to acquire seismic data in a much more efficient way and saves considerable acquisition time. However, it is necessary to separate these data into their conventionally acquired equivalent state. Luckily, we can simply treat the deblending problem as a noise attenuation problem because the blending noise has been performed to be incoherent in some domains such as common receiver, common offset domains. Multichannel matching pursuit (MCMP) is a lateral coherency based technique and has been widely used in a variety of seismic applications such as seismic trace decomposition and denoising seismic records. It decomposes the signals into a series of wavelets namely atoms, but the atom is just the best match to the average of multiple traces with the same scale factor, translation factor, frequency factor and phase parameter at each iteration, which is not in accord with the real seismic records. In this paper, we propose a new multichannel matching pursuit (MCMP) algorithm with directional features for simultaneous source separation in common receiver gathers. The new MCMP uses local lateral coherence as a constraint and utilizes the maximum semblance coefficient within a multidirectional window as the best direction at each iteration. To verify the effectiveness of this method, we use Ricker wavelet to synthetize a simultaneous source data set and sort the data to common receiver gathers. Comparing the deblending results with multidirectional vector median filter (MDVMF) method, the new MCMP preserves more useful seismic signals, but some individual useful signals are not reconstructed successfully probably because of the zero padding influence. The real data examples also prove that the new MCMP is effective in practice for deblending.

  12. Space-time decomposition of global Sea Surface Temperature variability using Multichannel Empirical Orthogonal Teleconnection analysis

    NASA Astrophysics Data System (ADS)

    Parmentier, B.; Neeti, N.; Eastman, R.

    2011-12-01

    With earth observation data, one of the primary concerns is the discovery of recurrent patterns over time. For example, the ENSO phenomenon is a major climatological pattern of global significance. As a spatial/two-dimensional extension of Singular Spectrum Analysis (SSA), Multichannel Singular Spectrum Analysis (MSSA) seeks to uncover the temporal evolution of recurrent space-time patterns within a specified time frame (known as the embedding dimension) by a method of spectral decomposition equivalent to Extended Principal Components Analysis. However, it suffers from the same limitations as PCA with regard to the propensity to develop components that are mixtures of multiple dominant patterns. In this paper we introduce a novel procedure we call Multichannel Empirical Orthogonal Teleconnection (MEOT) analysis as a simple extension of the logic of Empirical Orthogonal Teleconnections (EOT). A global sea surface temperature dataset spanning the 1982-2007 time period is utilized to explore the similarities and differences between MSSA and MEOT. The techniques are applied with a 13 month embedding dimension to extract spatio-temporal patterns that exhibit clear basis vectors in quadrature. Findings indicate that MEOT is capable of detecting more patterns in quadrature than MSSA. MEOT identifies three climate events as quadratures corresponding to the El Niño Southern Oscillation (ENSO), the Atlantic Meridional Mode (AMM) and the Atlantic Niño/ Tropical Southern Atlantic (TSA) mode. All of these climate events have phase change within a year. MSSA in contrast, only identified the ENSO event. Moreover, since MEOT does not suffer from a bi-orthogonality constraint, it is capable of extracting fewer mixed modes of variability than MSSA. Thus, results suggest a better identification and representation of individual climate events by the MEOT method.

  13. A simple approach to evaluate the kinetic rate constant for ATP synthesis in resting human skeletal muscle at 7 T.

    PubMed

    Ren, Jimin; Sherry, A Dean; Malloy, Craig R

    2016-09-01

    Inversion transfer (IT) is a well-established technique with multiple attractive features for analysis of kinetics. However, its application in measurement of ATP synthesis rate in vivo has lagged behind the more common saturation transfer (ST) techniques. One well-recognized issue with IT is the complexity of data analysis in comparison with much simpler analysis by ST. This complexity arises, in part, because the γ-ATP spin is involved in multiple chemical reactions and magnetization exchanges, whereas Pi is involved in a single reaction, Pi → γ-ATP. By considering the reactions involving γ-ATP only as a lumped constant, the rate constant for the reaction of physiological interest, kPi→γATP , can be determined. Here, we present a new IT data analysis method to evaluate kPi→γATP using data collected from resting human skeletal muscle at 7 T. The method is based on the basic Bloch-McConnell equation, which relates kPi→γATP to m˙Pi, the rate of Pi magnetization change. The kPi→γATP value is accessed from m˙Pi data by more familiar linear correlation approaches. For a group of human subjects (n = 15), the kPi→γATP value derived for resting calf muscle was 0.066 ± 0.017 s(-1) , in agreement with literature-reported values. In this study we also explored possible time-saving strategies to speed up data acquisition for kPi→γATP evaluation using simulations. The analysis indicates that it is feasible to carry out a (31) P IT experiment in about 10 min or less at 7 T with reasonable outcome in kPi→γATP variance for measurement of ATP synthesis in resting human skeletal muscle. We believe that this new IT data analysis approach will facilitate the wide acceptance of IT to evaluate ATP synthesis rate in vivo. Copyright © 2015 John Wiley & Sons, Ltd.

  14. Multichannel infrared fiber optic radiometer for controlled microwave heating

    NASA Astrophysics Data System (ADS)

    Drizlikh, S.; Zur, Albert; Katzir, Abraham

    1990-07-01

    An infrared fiberoptic multichannel radiometer was used for monitoring and controlling the temperature of samples in a microwave heating system. The temperature of water samples was maintained at about 40 °C, with a standard deviation of +/- 0.2°C and a maximum deviation of +/- 0.5°C. The temperature was monitored on the same time at several points on the surface and inside the sample. This novel controlled system is reliable and precise. Such system would be very useful for medical applications such as hypothermia and hyperthermi a.

  15. An experimental investigation of pulsed multichannel discharge across solid insulators

    NASA Technical Reports Server (NTRS)

    Lakdawala, V. K.; Ko, S. T.; Lee, J. H.

    1985-01-01

    An experimental study of pulsed surface flashover across a solid insulator in a vacuum is reported, with application of fast impulse voltages of a few tens of ns rise time and a few microsec tail time. Following the flashover voltage experiments, no visible degradation of the surface was found for the BaTiO3 sample, whereas for the TiO2 sample a distinct track mark could be seen where the flashover occurred. Three schemes for obtaining multichannel discharges were studied for plexiglass specimens, and results showed the number of shots to decrease as the number of channels increased.

  16. Multichannel Fabry-Perot spectrometer for infrared astronomy

    NASA Technical Reports Server (NTRS)

    Jennings, Donald E.; Boyle, R. J.

    1986-01-01

    A multichannel design which makes use of the radiation normally rejected in a Fabry-Perot spectrometer is described, with application to infrared astronomy. The present optical design minimizes the diameters of the etalon and optics. The use of spherical mirrors ensures that no radiation is lost through the entrance aperture, and the beams can be completely collimated at the etalon. Laboratory studies demonstrate that the ability to employ eight channels increases by a factor of four the flux integrated during a given time period compared with that of a single-channel instrument. The spectrometer is nondispersive, and the source can be imaged at each of several output spectral positions.

  17. van Hove singularities in disordered multichannel quantum wires and nanotubes

    NASA Astrophysics Data System (ADS)

    Hügle, S.; Egger, R.

    2002-11-01

    We present a theory for the van Hove singularity (VHS) in the tunneling density of states (TDOS) of disordered multichannel quantum wires, in particular multiwall carbon nanotubes. We assume close-by gates that screen off electron-electron interactions. Diagrammatic perturbation theory within the noncrossing approximation yields analytical expressions governing the disorder-induced broadening and shift of VHS's as new subbands are opened. This problem is nontrivial because the (lowest-order) Born approximation breaks down close to the VHS. Interestingly, compared to the bulk case, the boundary TDOS shows drastically altered VHS's, even in the clean limit.

  18. Development of multichannel low-energy neutron spectrometer

    SciTech Connect

    Arikawa, Y. Nagai, T.; Abe, Y.; Kojima, S.; Sakata, S.; Inoue, H.; Utsugi, M.; Iwasa, Y.; Sarukura, N.; Nakai, M.; Shiraga, H.; Fujioka, S.; Azechi, H.; Murata, T.

    2014-11-15

    A multichannel low-energy neutron spectrometer for down-scattered neutron (DSN) measurements in inertial confinement fusion (ICF) experiments has been developed. Our compact-size 256-channel lithium-glass-scintillator-based spectrometer has been implemented and tested in ICF experiments with the GEKKO XII laser. We have performed time calibration of the 256-channel analog-to-digital convertor system used for DSN measurements via X-ray pulse signals. We have clearly observed the DD-primary fusion neutron signal and have successfully studied the detector's impulse response. Our detector is soon to be implemented in future ICF experiments.

  19. Multi-channel Scaler Cards Improve Data Collection

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Scientists interested in exploring the intricacies and dynamics of Earth's climate and ecosystems continually need smaller, lighter instrumentation that can be placed onboard various sensing platforms, such as Unmanned Aerial Vehicles (UAVs). Responding to a need for improved data collection for remote atmospheric measurement systems, ASRC Aerospace Corporation, of Greenbelt, Maryland, developed a series of low-power, highly integrated, multichannel scaler (MCS) cards. The cards were designed to meet the needs of NASA's ground-based and airborne Light Detection and Ranging (LIDAR) photoncounting programs. They can rapidly collect thousands of data points during a continuous scan of the atmosphere.

  20. Multichannel demultiplexer/demodulator technologies for future satellite communication systems

    NASA Technical Reports Server (NTRS)

    Ivancic, William D.; Budinger, James M.; Staples, Edward J.; Abramovitz, Irwin; Courtois, Hector A.

    1992-01-01

    NASA-Lewis' Space Electronics Div. supports ongoing research in advanced satellite communication architectures, onboard processing, and technology development. Recent studies indicate that meshed VSAT (very small aperture terminal) satellite communication networks using FDMA (frequency division multiple access) uplinks and TDMA (time division multiplexed) downlinks are required to meet future communication needs. One of the critical advancements in such a satellite communication network is the multichannel demultiplexer/demodulator (MCDD). The progress is described which was made in MCDD development using either acousto-optical, optical, or digital technologies.

  1. Multichannel quantum-defect theory for slow atomic collisions

    SciTech Connect

    Gao Bo; Tiesinga, Eite; Williams, Carl J.; Julienne, Paul S.

    2005-10-15

    We present a multichannel quantum-defect theory for slow atomic collisions that takes advantages of the analytic solutions for the long-range potential and both the energy and angular momentum insensitivities of the short-range parameters. The theory provides an accurate and complete account of scattering processes, including shape and Feshbach resonances, in terms of a few parameters such as the singlet and triplet scattering lengths. As an example, results for {sup 23}Na-{sup 23}Na scattering are presented and compared to close-coupling calculations.

  2. Multichannel analysis of surface waves (MASW) - Active and passive methods

    USGS Publications Warehouse

    Park, C.B.; Miller, R.D.; Xia, J.; Ivanov, J.

    2007-01-01

    The conventional seismic approaches for near-surface investigation have usually been either high-resolution reflection or refraction surveys that deal with a depth range of a few tens to hundreds meters. Seismic signals from these surveys consist of wavelets with frequencies higher than 50 Hz. The multichannel analysis of surface waves (MASW) method deals with surface waves in the lower frequencies (e.g., 1-30 Hz) and uses a much shallower depth range of investigation (e.g., a few to a few tens of meters). ?? 2007 Society of Exploration Geophysicists.

  3. A multichannel biotelemetry transmitter utilizing a PCM subcarrier

    NASA Technical Reports Server (NTRS)

    Fryer, T. B.; Westbrook, R. M.

    1974-01-01

    Making use of the currently available integrated circuits, a miniature PCM telemetry system operating from one miniature 9-volt battery and drawing less than 5 milliamps has been constructed. The use of this PCM telemetry signal not only provides accurate data transmission, but requires a minimum of RF bandwidth. The serial format that results from multiplexing the input data allows the use of a single channel recorder with its cost savings over a multichannel tape recorder. An additional benefit of the PCM encoding is that the data is in digital format and is directly suitable for computer use.

  4. A multi-channel instrumentation system for biosignal recording.

    PubMed

    Yu, Hong; Li, Pengfei; Xiao, Zhiming; Peng, Chung-Ching; Bashirullah, Rizwan

    2008-01-01

    This paper reports a highly integrated battery operated multi-channel instrumentation system intended for physiological signal recording. The mixed signal IC has been fabricated in standard 0.5microm 5V 3M-2P CMOS process and features 32 instrumentation amplifiers, four 8b SAR ADCs, a wireless power interface with Li-ion battery charger, low power bidirectional telemetry and FSM controller with power gating control for improved energy efficiency. The chip measures 3.2mm by 4.8mm and dissipates approximately 2.1mW when fully operational.

  5. Architecture of the multichannel data-driven ASIC

    NASA Astrophysics Data System (ADS)

    Normanov, D. D.; Atkin, E. V.

    2016-02-01

    The development architecture of a multichannel data-driven ASIC is presented. It provides the selection of useful events at an early stage of reading out detector signals. The architecture is based on fast cross-point switches of analog signals, followed by their digitization by a limited set of ADCs and high-speed output data serialization. Such approach reduces the number of subsequent ADCs as well as digital processing channels. That leads to lower power consumption and chip area. The results of a prototype ASIC development, based on this architecture and intended for the CBM experiment at FAIR, are given.

  6. A new multichannel interferometer system on HL-2A

    SciTech Connect

    Zhou, Y.; Deng, Z. C.; Liu, Z. T.; Yi, J.; Tang, Y. W.; Gao, B. Y.; Tian, C. L.; Li, Y. G.; Ding, X. T.

    2007-11-15

    A new multichannel HCN interferometer has been developed on HL-2A tokamak, which is characterized by two techniques: (1) the wave-guide HCN laser with cavity length of 6 m to increase the optical resource power and (2) high response room temperature waveguide Schottky diode detectors to obtain good beat signal. The space resolution is 7 cm by the use of focusing metal mirrors mounted on the vacuum chamber and a compensated optical system. In the 2006 experiment campaign, this new interferometer has been applied for plasma density profile and density sawtooth measurement.

  7. Multichannel array diagnosis using noise cross-correlation.

    PubMed

    Brooks, Laura A; Gerstoft, Peter; Knobles, David P

    2008-10-01

    A practical application of noise cross-correlation for the diagnosis of a multichannel ocean hydrophone array is derived. Acoustic data were recorded on a horizontal line array on the New Jersey Shelf while Tropical Storm Ernesto passed through. Results obtained from active source measurements reveal that signals from several hydrophones, which were recorded on certain channels before the storm, are recorded on different channels after the storm. Noise cross-correlation of data recorded during the storm show when, and in what manner, these changes took place.

  8. Resource allocation for multichannel broadcasting visible light communication

    NASA Astrophysics Data System (ADS)

    Le, Nam-Tuan; Jang, Yeong Min

    2015-11-01

    Visible light communication (VLC), which offers the possibility of using light sources for both illumination and data communications simultaneously, will be a promising incorporation technique with lighting applications. However, it still remains some challenges especially coverage because of field-of-view limitation. In this paper, we focus on this issue by suggesting a resource allocation scheme for VLC broadcasting system. By using frame synchronization and a network calculus QoS approximation, as well as diversity technology, the proposed VLC architecture and QoS resource allocation for the multichannel-broadcasting MAC (medium access control) protocol can solve the coverage limitation problem and the link switching problem of exhibition service.

  9. SAR Reduction in 7T C-Spine Imaging Using a “Dark Modes” Transmit Array Strategy

    PubMed Central

    Eryaman, Yigitcan; Guerin, Bastien; Keil, Boris; Mareyam, Azma; Herraiz, Joaquin L.; Kosior, Robert K.; Martin, Adrian; Torrado-Carvajal, Angel; Malpica, Norberto; Hernandez-Tamames, Juan A.; Schiavi, Emanuele; Adalsteinsson, Elfar; Wald, Lawrence L.

    2016-01-01

    Purpose Local specific absorption rate (SAR) limits many applications of parallel transmit (pTx) in ultra high-field imaging. In this Note, we introduce the use of an array element, which is intentionally inefficient at generating spin excitation (a “dark mode”) to attempt a partial cancellation of the electric field from those elements that do generate excitation. We show that adding dipole elements oriented orthogonal to their conventional orientation to a linear array of conventional loop elements can lower the local SAR hotspot in a C-spine array at 7 T. Methods We model electromagnetic fields in a head/torso model to calculate SAR and excitation B1+ patterns generated by conventional loop arrays and loop arrays with added electric dipole elements. We utilize the dark modes that are generated by the intentional and inefficient orientation of dipole elements in order to reduce peak 10g local SAR while maintaining excitation fidelity. Results For B1+ shimming in the spine, the addition of dipole elements did not significantly alter the B1+ spatial pattern but reduced local SAR by 36%. Conclusion The dipole elements provide a sufficiently complimentary B1+ and electric field pattern to the loop array that can be exploited by the radiofrequency shimming algorithm to reduce local SAR. PMID:24753012

  10. Magnetic resonance thermometry at 7T for real-time monitoring and correction of ultrasound induced mild hyperthermia.

    PubMed

    Fite, Brett Z; Liu, Yu; Kruse, Dustin E; Caskey, Charles F; Walton, Jeffrey H; Lai, Chun-Yen; Mahakian, Lisa M; Larrat, Benoit; Dumont, Erik; Ferrara, Katherine W

    2012-01-01

    While Magnetic Resonance Thermometry (MRT) has been extensively utilized for non-invasive temperature measurement, there is limited data on the use of high field (≥7T) scanners for this purpose. MR-guided Focused Ultrasound (MRgFUS) is a promising non-invasive method for localized hyperthermia and drug delivery. MRT based on the temperature sensitivity of the proton resonance frequency (PRF) has been implemented in both a tissue phantom and in vivo in a mouse Met-1 tumor model, using partial parallel imaging (PPI) to speed acquisition. An MRgFUS system capable of delivering a controlled 3D acoustic dose during real time MRT with proportional, integral, and derivative (PID) feedback control was developed and validated. Real-time MRT was validated in a tofu phantom with fluoroptic temperature measurements, and acoustic heating simulations were in good agreement with MR temperature maps. In an in vivo Met-1 mouse tumor, the real-time PID feedback control is capable of maintaining the desired temperature with high accuracy. We found that real time MR control of hyperthermia is feasible at high field, and k-space based PPI techniques may be implemented for increasing temporal resolution while maintaining temperature accuracy on the order of 1°C.

  11. Investigation of the neurovascular coupling in positive and negative BOLD responses in human brain at 7 T.

    PubMed

    Huber, Laurentius; Goense, Jozien; Kennerley, Aneurin J; Ivanov, Dimo; Krieger, Steffen N; Lepsien, Jöran; Trampel, Robert; Turner, Robert; Möller, Harald E

    2014-08-15

    Decreases in stimulus-dependent blood oxygenation level dependent (BOLD) signal and their underlying neurovascular origins have recently gained considerable interest. In this study a multi-echo, BOLD-corrected vascular space occupancy (VASO) functional magnetic resonance imaging (fMRI) technique was used to investigate neurovascular responses during stimuli that elicit positive and negative BOLD responses in human brain at 7 T. Stimulus-induced BOLD, cerebral blood volume (CBV), and cerebral blood flow (CBF) changes were measured and analyzed in 'arterial' and 'venous' blood compartments in macro- and microvasculature. We found that the overall interplay of mean CBV, CBF and BOLD responses is similar for tasks inducing positive and negative BOLD responses. Some aspects of the neurovascular coupling however, such as the temporal response, cortical depth dependence, and the weighting between 'arterial' and 'venous' contributions, are significantly different for the different task conditions. Namely, while for excitatory tasks the BOLD response peaks at the cortical surface, and the CBV change is similar in cortex and pial vasculature, inhibitory tasks are associated with a maximum negative BOLD response in deeper layers, with CBV showing strong constriction of surface arteries and a faster return to baseline. The different interplays of CBV, CBF and BOLD during excitatory and inhibitory responses suggests different underlying hemodynamic mechanisms.

  12. Functional magnetic resonance imaging of the rat cerebellum during electrical stimulation of the fore- and hindpaw at 7 T

    NASA Astrophysics Data System (ADS)

    Peeters, Ronald; Verhoye, Marleen; Vos, Bart; De Schutter, Erik; Van der Linden, Anne-Marie

    1999-05-01

    Blood oxygenation level dependent contrast (BOLD) functional MRI responses at 7T were observed in the cerebellum of alpha- chloralose anesthetized rats in response to innocuous electrical stimulation of a forepaw or hindpaw. The responses were imaged in both coronal and sagittal slices which allowed for a clear delineation and localization of the observed activations. We demonstrate the validity of our fMRI protocol by imaging the responses in somatosensory cortex to the same stimuli and by showing a high level of reproducibility of the cerebellar responses. Widespread bilateral activations were found with mainly a patchy and medio-lateral band organization, more pronounced ipsilaterally. There was no overlap between the cerebellar activations caused by forepaw or hindpaw stimulation. Most remarkable was the overall horizontal organization of these responses: for both stimulation paradigms the patches and bands of activation were roughly positioned in either a cranial or caudal plane running antero-posteriorly through the whole cerebellum. This is the first fMRI study in the cerebellum of the rat. We relate our findings to the known projection patterns found with other techniques and to human fMRI studies. The horizontal organization found wasn't observed before in other studies using other techniques.

  13. Representation of Sound Objects within Early-Stage Auditory Areas: A Repetition Effect Study Using 7T fMRI.

    PubMed

    Da Costa, Sandra; Bourquin, Nathalie M-P; Knebel, Jean-François; Saenz, Melissa; van der Zwaag, Wietske; Clarke, Stephanie

    2015-01-01

    Environmental sounds are highly complex stimuli whose recognition depends on the interaction of top-down and bottom-up processes in the brain. Their semantic representations were shown to yield repetition suppression effects, i. e. a decrease in activity during exposure to a sound that is perceived as belonging to the same source as a preceding sound. Making use of the high spatial resolution of 7T fMRI we have investigated the representations of sound objects within early-stage auditory areas on the supratemporal plane. The primary auditory cortex was identified by means of tonotopic mapping and the non-primary areas by comparison with previous histological studies. Repeated presentations of different exemplars of the same sound source, as compared to the presentation of different sound sources, yielded significant repetition suppression effects within a subset of early-stage areas. This effect was found within the right hemisphere in primary areas A1 and R as well as two non-primary areas on the antero-medial part of the planum temporale, and within the left hemisphere in A1 and a non-primary area on the medial part of Heschl's gyrus. Thus, several, but not all early-stage auditory areas encode the meaning of environmental sounds. PMID:25938430

  14. Representation of Sound Objects within Early-Stage Auditory Areas: A Repetition Effect Study Using 7T fMRI

    PubMed Central

    Da Costa, Sandra; Bourquin, Nathalie M.-P.; Knebel, Jean-François; Saenz, Melissa; van der Zwaag, Wietske; Clarke, Stephanie

    2015-01-01

    Environmental sounds are highly complex stimuli whose recognition depends on the interaction of top-down and bottom-up processes in the brain. Their semantic representations were shown to yield repetition suppression effects, i. e. a decrease in activity during exposure to a sound that is perceived as belonging to the same source as a preceding sound. Making use of the high spatial resolution of 7T fMRI we have investigated the representations of sound objects within early-stage auditory areas on the supratemporal plane. The primary auditory cortex was identified by means of tonotopic mapping and the non-primary areas by comparison with previous histological studies. Repeated presentations of different exemplars of the same sound source, as compared to the presentation of different sound sources, yielded significant repetition suppression effects within a subset of early-stage areas. This effect was found within the right hemisphere in primary areas A1 and R as well as two non-primary areas on the antero-medial part of the planum temporale, and within the left hemisphere in A1 and a non-primary area on the medial part of Heschl’s gyrus. Thus, several, but not all early-stage auditory areas encode the meaning of environmental sounds. PMID:25938430

  15. A 16-Channel Receive, Forced Current Excitation Dual-Transmit Coil for Breast Imaging at 7T

    PubMed Central

    By, Samantha; Rispoli, Joseph V.; Cheshkov, Sergey; Dimitrov, Ivan; Cui, Jiaming; Seiler, Stephen; Goudreau, Sally; Malloy, Craig; Wright, Steven M.; McDougall, Mary Preston

    2014-01-01

    Purpose To enable high spatial and temporal breast imaging resolution via combined use of high field MRI, array coils, and forced current excitation (FCE) multi channel transmit. Materials and Methods A unilateral 16-channel receive array insert was designed for use in a transmit volume coil optimized for quadrature operation with dual-transmit RF shimming at 7T. Signal-to-noise ratio (SNR) maps, g-factor maps, and high spatial and temporal resolution in vivo images were acquired to demonstrate the utility of the coil architecture. Results The dual-transmit FCE coil provided homogeneous excitation and the array provided an increase in average SNR of 3.3 times (max 10.8, min 1.5) compared to the volume coil in transmit/receive mode. High resolution accelerated in vivo breast imaging demonstrated the ability to achieve isotropic spatial resolution of 0.5 mm within clinically relevant 90 s scan times, as well as the ability to perform 1.0 mm isotropic resolution imaging, 7 s per dynamics, with the use of bidirectional SENSE acceleration of up to R = 9. Conclusion The FCE design of the transmit coil easily accommodates the addition of a sixteen channel array coil. The improved spatial and temporal resolution provided by the high-field array coil with FCE dual-channel transmit will ultimately be beneficial in lesion detection and characterization. PMID:25420018

  16. Magnetic Resonance Thermometry at 7T for Real-Time Monitoring and Correction of Ultrasound Induced Mild Hyperthermia

    PubMed Central

    Fite, Brett Z.; Liu, Yu; Kruse, Dustin E.; Caskey, Charles F.; Walton, Jeffrey H.; Lai, Chun-Yen; Mahakian, Lisa M.; Larrat, Benoit; Dumont, Erik; Ferrara, Katherine W.

    2012-01-01

    While Magnetic Resonance Thermometry (MRT) has been extensively utilized for non-invasive temperature measurement, there is limited data on the use of high field (≥7T) scanners for this purpose. MR-guided Focused Ultrasound (MRgFUS) is a promising non-invasive method for localized hyperthermia and drug delivery. MRT based on the temperature sensitivity of the proton resonance frequency (PRF) has been implemented in both a tissue phantom and in vivo in a mouse Met-1 tumor model, using partial parallel imaging (PPI) to speed acquisition. An MRgFUS system capable of delivering a controlled 3D acoustic dose during real time MRT with proportional, integral, and derivative (PID) feedback control was developed and validated. Real-time MRT was validated in a tofu phantom with fluoroptic temperature measurements, and acoustic heating simulations were in good agreement with MR temperature maps. In an in vivo Met-1 mouse tumor, the real-time PID feedback control is capable of maintaining the desired temperature with high accuracy. We found that real time MR control of hyperthermia is feasible at high field, and k-space based PPI techniques may be implemented for increasing temporal resolution while maintaining temperature accuracy on the order of 1°C. PMID:22536396

  17. Representation of Sound Objects within Early-Stage Auditory Areas: A Repetition Effect Study Using 7T fMRI.

    PubMed

    Da Costa, Sandra; Bourquin, Nathalie M-P; Knebel, Jean-François; Saenz, Melissa; van der Zwaag, Wietske; Clarke, Stephanie

    2015-01-01

    Environmental sounds are highly complex stimuli whose recognition depends on the interaction of top-down and bottom-up processes in the brain. Their semantic representations were shown to yield repetition suppression effects, i. e. a decrease in activity during exposure to a sound that is perceived as belonging to the same source as a preceding sound. Making use of the high spatial resolution of 7T fMRI we have investigated the representations of sound objects within early-stage auditory areas on the supratemporal plane. The primary auditory cortex was identified by means of tonotopic mapping and the non-primary areas by comparison with previous histological studies. Repeated presentations of different exemplars of the same sound source, as compared to the presentation of different sound sources, yielded significant repetition suppression effects within a subset of early-stage areas. This effect was found within the right hemisphere in primary areas A1 and R as well as two non-primary areas on the antero-medial part of the planum temporale, and within the left hemisphere in A1 and a non-primary area on the medial part of Heschl's gyrus. Thus, several, but not all early-stage auditory areas encode the meaning of environmental sounds.

  18. Multichannel biomedical time series clustering via hierarchical probabilistic latent semantic analysis.

    PubMed

    Wang, Jin; Sun, Xiangping; Nahavandi, Saeid; Kouzani, Abbas; Wu, Yuchuan; She, Mary

    2014-11-01

    Biomedical time series clustering that automatically groups a collection of time series according to their internal similarity is of importance for medical record management and inspection such as bio-signals archiving and retrieval. In this paper, a novel framework that automatically groups a set of unlabelled multichannel biomedical time series according to their internal structural similarity is proposed. Specifically, we treat a multichannel biomedical time series as a document and extract local segments from the time series as words. We extend a topic model, i.e., the Hierarchical probabilistic Latent Semantic Analysis (H-pLSA), which was originally developed for visual motion analysis to cluster a set of unlabelled multichannel time series. The H-pLSA models each channel of the multichannel time series using a local pLSA in the first layer. The topics learned in the local pLSA are then fed to a global pLSA in the second layer to discover the categories of multichannel time series. Experiments on a dataset extracted from multichannel Electrocardiography (ECG) signals demonstrate that the proposed method performs better than previous state-of-the-art approaches and is relatively robust to the variations of parameters including length of local segments and dictionary size. Although the experimental evaluation used the multichannel ECG signals in a biometric scenario, the proposed algorithm is a universal framework for multichannel biomedical time series clustering according to their structural similarity, which has many applications in biomedical time series management.

  19. 47 CFR 76.613 - Interference from a multichannel video programming distributor (MVPD).

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 4 2012-10-01 2012-10-01 false Interference from a multichannel video programming distributor (MVPD). 76.613 Section 76.613 Telecommunication FEDERAL COMMUNICATIONS COMMISSION....613 Interference from a multichannel video programming distributor (MVPD). (a) Harmful interference...

  20. 47 CFR 76.613 - Interference from a multichannel video programming distributor (MVPD).

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 4 2014-10-01 2014-10-01 false Interference from a multichannel video programming distributor (MVPD). 76.613 Section 76.613 Telecommunication FEDERAL COMMUNICATIONS COMMISSION....613 Interference from a multichannel video programming distributor (MVPD). (a) Harmful interference...

  1. 47 CFR 76.613 - Interference from a multichannel video programming distributor (MVPD).

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 4 2011-10-01 2011-10-01 false Interference from a multichannel video programming distributor (MVPD). 76.613 Section 76.613 Telecommunication FEDERAL COMMUNICATIONS COMMISSION....613 Interference from a multichannel video programming distributor (MVPD). (a) Harmful interference...

  2. 47 CFR 76.613 - Interference from a multichannel video programming distributor (MVPD).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Interference from a multichannel video programming distributor (MVPD). 76.613 Section 76.613 Telecommunication FEDERAL COMMUNICATIONS COMMISSION....613 Interference from a multichannel video programming distributor (MVPD). (a) Harmful interference...

  3. 47 CFR 76.613 - Interference from a multichannel video programming distributor (MVPD).

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 4 2013-10-01 2013-10-01 false Interference from a multichannel video programming distributor (MVPD). 76.613 Section 76.613 Telecommunication FEDERAL COMMUNICATIONS COMMISSION....613 Interference from a multichannel video programming distributor (MVPD). (a) Harmful interference...

  4. Multi-channel access technology based on wavelength division multiplexing in wireless UV communication mesh network

    NASA Astrophysics Data System (ADS)

    Zhao, Tai-fei; Zhang, Ai-li; Xue, Rong-li

    2013-05-01

    In this paper, the multi-channel access technology of wavelength division multiplexing (WDM) in the wireless ultraviolet (UV) scattering communication is studied. A multi-interface and multi-channel device is deployed in each UV transceiver node. The band-pass filter is configured in the receiving node so as to realize the multi-channel access by use of the UV WDM technology. Both the UV communication node model and the UV channel model are established. Three types of UV no-line-of-sight (NLOS) multi-channel communications are simulated in the mesh topologies with NS2. The results show that the UV multi-channel access technology can increase network throughput effectively with using WDM.

  5. Single and Multi-Channel Carbon-based Quantum Dragons

    NASA Astrophysics Data System (ADS)

    Inkoom, Godfred; Abdurazakov, Omadillo; Novotny, Mark

    2015-03-01

    In the coherent regime for electrical conductance measurements, two semi-infinite leads are connected to a finite nanostructure, and the nano-device conductance is calculated using the Landauer formula. Any channel k that has transmission for electrons with energy E, \\calTk (E) =1 contributes the conductance quantum G0 = 2e2 / h . Any nano-device with at least one \\calTk (E) =1 is called a quantum dragon. The transmission probability \\calTk (E) can be obtained from the solution of the time-independent Schrödinger equation. Uniform leads connected to armchair single-walled carbon nanotubes (SWCNTs) have calT (E) =1, while when connected to zigzag SWCNT the calT (E) is less than unity. Appropriately dimerized leads connected to zigzag SWCNTs are quantum dragons, while when connected to armchair SWCNTs calT (E) is less than unity. We have generalized the matrix method and mapping methods of in order to investigate SWCNTs that can be multi-channel quantum dragons. For example, one can use armchair SWCNT leads to connect to an armchair SWCNT to try to produce a multi-channel quantum dragon. Supported in part by NSF Grant DMR-1206233.

  6. Multi-channel fiber photometry for population neuronal activity recording.

    PubMed

    Guo, Qingchun; Zhou, Jingfeng; Feng, Qiru; Lin, Rui; Gong, Hui; Luo, Qingming; Zeng, Shaoqun; Luo, Minmin; Fu, Ling

    2015-10-01

    Fiber photometry has become increasingly popular among neuroscientists as a convenient tool for the recording of genetically defined neuronal population in behaving animals. Here, we report the development of the multi-channel fiber photometry system to simultaneously monitor neural activities in several brain areas of an animal or in different animals. In this system, a galvano-mirror modulates and cyclically couples the excitation light to individual multimode optical fiber bundles. A single photodetector collects excited light and the configuration of fiber bundle assembly and the scanner determines the total channel number. We demonstrated that the system exhibited negligible crosstalk between channels and optical signals could be sampled simultaneously with a sample rate of at least 100 Hz for each channel, which is sufficient for recording calcium signals. Using this system, we successfully recorded GCaMP6 fluorescent signals from the bilateral barrel cortices of a head-restrained mouse in a dual-channel mode, and the orbitofrontal cortices of multiple freely moving mice in a triple-channel mode. The multi-channel fiber photometry system would be a valuable tool for simultaneous recordings of population activities in different brain areas of a given animal and different interacting individuals.

  7. Time transfer using multi-channel GPS receivers.

    PubMed

    Levine, J

    1999-01-01

    This report is on time transfer experiments using a Global Positioning System (GPS) receiver constructed using a commercial GPS "engine" and a standard PC. The receiver measures the time difference between the local clock and a 1 pps signal synchronized to GPS time using data from up to 8 satellites. The receiver also reports the difference between GPS time as estimated using each of the satellites being tracked and the composite output pulses that have a rate of 1 Hz (1 pps signal). These data can be used to construct the standard 13-minute tracks as defined in the BIPM standard; the same data also can be averaged in other ways that make better use of the multi-channel capabilities of the hardware. The 13-minute averages can be directly compared with standard time-transfer receivers using common-view analysis. The results of the tests suggest that the methods currently used for national and international time and frequency coordination should be re-examined, and an alternative approach based on multi-channel receivers is suggested that should be more flexible, simpler, and easier to operate than the current system. PMID:18238436

  8. International Live Endoscopic Multichannel Demonstration Using Superfast Broadband Internet Connections

    PubMed Central

    Lee, Sang Pyo; Lee, Hang Lak; Choi, Ho Soon; Joe, Inwhee; Shimizu, Shuji

    2012-01-01

    Background/Aims Telemedicine is a convenient and efficient tool for remote education in various fields. The telemedicine system can also be used to educate doctors and medical students. The aim of our study was to establish the effectiveness of the telemedical system for use in a live endoscopic multichannel demonstration conference and to test the effectiveness and usefulness of a multicenter-based live endoscopic demonstration through live, interactive, high resolution video transmission using advanced networks and the digital video transport system (DVTS). Methods This study is a prospective multicenter pilot study. A live demonstration of an endoscopic submucosal dissection (ESD) and an endoscopic retrograde cholangiopancreatography (ERCP) using advanced network technology was performed. Results The DVTS successfully transmitted uncompressed, high-resolution, digital lectures with endoscopy video during a multichannel endoscopic live demonstration of ESD and ERCP over multiple advanced networks. The overall satisfaction rating when the endoscopic lecture demonstration was performed by combining DVTS was generally good. Conclusions We believe that a multicenter-based live endoscopic demonstration is a very effective conferencing method when using advanced networks and DVTS. PMID:22741135

  9. Optical multichannel analyzer techniques for high resolution optical spectroscopy

    SciTech Connect

    Chao, J.L.

    1980-06-01

    The development of optical multichannel analyzer techniques for UV/VIS spectroscopy is presented. The research focuses on the development of spectroscopic techniques for measuring high resolution spectral lineshape functions from the exciton phosphorescence in H/sub 2/-1,2,4,5-tetrachlorobenzene. It is found that the temperature dependent frequency shifts and widths confirm a theoretical model based on an exchange theory. The exchange of low energy phonon modes which couple with excited state exciton transitions is shown to display the proper temperature dependent behavior. In addition to the techniques for using the optical multichannel analyzer (OMA) to perform low light level target integration, the use of the OMA for capturing spectral information in transient pulsed laser applications is discussed. An OMP data acquisition system developed for real-time signal processng is described. Both hardware and software interfacing considerations for control and data acquisition by a microcomputer are described. The OMA detector is described in terms of the principles behind its photoelectron detection capabilities and its design is compared with other optoelectronic devices.

  10. A duple watermarking strategy for multi-channel quantum images

    NASA Astrophysics Data System (ADS)

    Yan, Fei; Iliyasu, Abdullah M.; Sun, Bo; Venegas-Andraca, Salvador E.; Dong, Fangyan; Hirota, Kaoru

    2015-05-01

    Utilizing a stockpile of efficient transformations consisting of channel of interest, channel swapping, and quantum Fourier transforms, a duple watermarking strategy on multi-channel quantum images is proposed. It embeds the watermark image both into the spatial domain and the frequency domain of the multi-channel quantum carrier image, while also providing a quantum measurement-based algorithm to generate an unknown key that is used to protect the color information, which accompanies another key that is mainly used to scramble the spatial content of the watermark image in order to further safeguard the copyright of the carrier image. Simulation-based experiments using a watermark logo and nine building images as watermark image and carrier images, respectively, offer a duple protection for the copyright of carrier images in terms of the visible quality of the watermarked images. The proposed stratagem advances available literature in the quantum watermarking research field and sets the stage for the applications aimed at quantum data protection.

  11. An Optimal Pulse System Design by Multichannel Sensors Fusion.

    PubMed

    Wang, Dimin; Zhang, David; Lu, Guangming

    2016-03-01

    Pulse diagnosis, recognized as an important branch of traditional Chinese medicine (TCM), has a long history for health diagnosis. Certain features in the pulse are known to be related with the physiological status, which have been identified as biomarkers. In recent years, an electronic equipment is designed to obtain the valuable information inside pulse. Single-point pulse acquisition platform has the benefit of low cost and flexibility, but is time consuming in operation and not standardized in pulse location. The pulse system with a single-type sensor is easy to implement, but is limited in extracting sufficient pulse information. This paper proposes a novel system with optimal design that is special for pulse diagnosis. We combine a pressure sensor with a photoelectric sensor array to make a multichannel sensor fusion structure. Then, the optimal pulse signal processing methods and sensor fusion strategy are introduced for the feature extraction. Finally, the developed optimal pulse system and methods are tested on pulse database acquired from the healthy subjects and the patients known to be afflicted with diabetes. The experimental results indicate that the classification accuracy is increased significantly under the optimal design and also demonstrate that the developed pulse system with multichannel sensors fusion is more effective than the previous pulse acquisition platforms. PMID:25608317

  12. Phoneme recognition and confusions with multichannel cochlear implants: vowels.

    PubMed

    Välimaa, Taina T; Määttä, Taisto K; Löppönen, Heikki J; Sorri, Martti J

    2002-10-01

    The aim of this study was to investigate how postlingually severely or profoundly hearing-impaired adults relearn to recognize vowels after receiving multichannel cochlear implants. Vowel recognition of 19 Finnish-speaking subjects was studied for a minimum of 6 months and a maximum of 24 months using an open-set nonsense-syllable test in a prospective repeated-measure design. The responses were coded for phoneme errors, and 95% confidence intervals for recognition and confusions were calculated. The average vowel recognition was 68% (95% confidence interval = 66-70%) 6 months after switch-on and 80% (95% confidence interval = 78-82%) 24 months after switch-on. The vowels [ae], [u], [i], [o], and [a] were the easiest to recognize, and the vowels [y], [e], and [ø] were the most difficult. In conclusion, adaptation to electrical hearing using a multichannel cochlear implant was achieved well; but for at least 2 years, given two vowels with either F1 or F2 at roughly the some frequencies, confusions were drawn more towards the closest vowel with the next highest F1 or F2.

  13. Phoneme recognition and confusions with multichannel cochlear implants: consonants.

    PubMed

    Välimaa, Taina T; Määttä, Taisto K; Löppönen, Heikki J; Sorri, Martti J

    2002-10-01

    The aim of this study was to investigate how postlingually severely or profoundly hearing-impaired adults relearn to recognize consonants after receiving multichannel cochlear implants. Consonant recognition of 19 Finnish-speaking subjects was studied for a minimum of 6 months and a maximum of 24 months using an open-set nonsense-syllable test in a prospective repeated-measure design. Responses were coded for phoneme errors, and proportions of correct responses and 95% confidence intervals were calculated for recognition and confusions. Two years after the switch-on, the mean recognition of consonants was 71% (95% confidence interval = 68-73%). The manner of articulation was easier to classify than the place of articulation, and the consonants [s], [r], [k], [t], [p], [n], and [j] were easier to recognize than [h], [m], [l], and [v]. Adaptation to electrical hearing with a multichannel cochlear implant was successful, but consonants with alveolar, palatal, or velar transitions (high F2) were better recognized than consonants with labial transitions (low F2). The locus of the F2 transitions of the consonants with better recognition was at the frequencies 1.5-2 kHz, whereas the locus of the F2 transitions of the consonants with poorer recognition was at 1.2-1.4 kHz. A tendency to confuse consonants with the closest consonant with higher F2 transition was also noted.

  14. Multichannel electrotactile feedback for simultaneous and proportional myoelectric control

    NASA Astrophysics Data System (ADS)

    Patel, Gauravkumar K.; Dosen, Strahinja; Castellini, Claudio; Farina, Dario

    2016-10-01

    Objective. Closing the loop in myoelectric prostheses by providing artificial somatosensory feedback to the user is an important need for prosthetic users. Previous studies investigated feedback strategies in combination with the control of one degree of freedom of simple grippers. Modern hands, however, are sophisticated multifunction systems. In this study, we assessed multichannel electrotactile feedback integrated with an advanced method for the simultaneous and proportional control of individual fingers of a dexterous hand. Approach. The feedback used spatial and frequency coding to provide information on the finger positions (normalized flexion angles). A comprehensive set of conditions have been investigated in 28 able-bodied subjects, including feedback modalities (visual, electrotactile and no feedback), control tasks (fingers and grasps), systems (virtual and real hand), control methods (ideal and realistic) and range of motion (low and high). The task for the subjects was to operate the hand using closed-loop myoelectric control and generate the desired movement (e.g., selected finger or grasp at a specific level of closure). Main results. The subjects could perceive the multichannel and multivariable electrotactile feedback and effectively exploit it to improve the control performance with respect to open-loop grasping. The improvement however depended on the reliability of the feedforward control, with less consistent control exhibiting performance trends that were more complex across the conditions. Significance. The results are promising for the potential application of advanced feedback to close the control loop in sophisticated prosthetic systems.

  15. Low noise multichannel circuits for physics and biology applications

    NASA Astrophysics Data System (ADS)

    Grybos, Pawel

    2005-09-01

    Experimental techniques in physics, material science, biology and medicine want to gain profit from the advantages of the VLSI technology by using a new generation of electronic measurement systems based on parallel signal processing from the multielement sensors. In most cases key problems for building such system are multichannel mixed-mode Application Specific Integrated Circuits, which are capable to process small amplitude signals from multielement sensor. In this class of integrated circuits several important problems like power limitation, low level of noise, good matching performance and crosstalk effects must be solved simultaneously. This presentation shows two ASICs which, given the original solutions implemented and their universal properties, can be used in different applications and are significant milestones in experimental techniques. The first presented ASIC is the 64-channel charge amplifier with binary readout architecture for a low energy X-ray imaging techniques. This integrated circuit connected to silicon strip detector can be used in powder diffractometry and then it reduces the measurement time by two order of magnitude. The second presented ASIC is multichannel low noise readout for extracellular neural recording, which is able to cope with extracellular neuronal recording for the systems comprising several hundreds of electrodes. Important steps forward in this design are a novel solution for band-pass filters for low frequency range, which follow requirements for good matching, low power and small silicon area. This ASIC can be used to monitor the neural activity of such complicated system like retina or brain.

  16. Neurodegenerative evidences during early onset of depression in CMS rats as detected by proton magnetic resonance spectroscopy at 7 T.

    PubMed

    Hemanth Kumar, B S; Mishra, Sushanta Kumar; Rana, Poonam; Singh, Sadhana; Khushu, Subash

    2012-06-15

    Depression is a complex psychiatric disorder characterized by anhedonia and feeling of sadness and chronic mild stress (CMS) seems to be a valuable animal model of depression. CMS animal model was induced and validated using behavioral studies. In the present study we investigated the neuro-metabolite changes occurring in prefrontal cortex and hippocampus during the onset of depression, in CMS rat model using in vivo proton magnetic resonance spectroscopy ((1)H MRS) at field strength of 7 T. Results showed that CMS caused depression-like behavior in rats, as indicated by the decrease in sucrose consumption and locomotor activity. (1)H MRS was performed in both control and CMS rats (n=10, in each group) and the quantitative assessment of the neurometabolites was done using LC model. Relative concentrations of all the metabolites along with the macromolecules were calculated for analysis. The results revealed a significant decrease of glutamate (Glu), glutamine (Gln), NAA+NAAG, Glx and GABA levels in both hippocampus and prefrontal cortex of CMS animals and an elevated level of myo-ionisitol (mI) and taurine (Tau) was observed only in hippocampus. These metabolite fluctuations revealed by proton MRS indicate that there might be change in the neuronal integrity of the glial cells and neurons within prefrontal cortex and hippocampus in CMS model of depression. The present study also suggests that there may be a degenerative process concerning the brain morphology in the CMS rats. The overall finding using (1)H MRS suggests that, there might be a major role of the glia and neuron in the onset of depression. PMID:22449862

  17. Differential passage of gadolinium through the mouse inner ear barriers evaluated with 4.7T MRI.

    PubMed

    Zou, Jing; Zhang, Weikai; Poe, Dennis; Zhang, Ya; Ramadan, Usama Abo; Pyykkö, Ilmari

    2010-01-01

    Magnetic resonance imaging (MRI), supplemented by contrast agents, is a powerful tool that can be used to visualise the structures of the inner ear in vivo and assess some aspects of physiology, such as the permeability of agents through membranes. The mouse is an excellent animal species for investigating human diseases, including hearing loss but detailed MRI studies with contrast have not been reported. In this work, we aimed to demonstrate the limits of MR imaging resolution of the fine inner ear structures in the mouse and to explore the permeability of the intracochlear barriers to gadolinium-tetra-azacyclo-dodecane-tetra-acetic acid (Gd-DOTA) administered by intravenous injection (IV) or intratympanic (IT) routes. Twenty-three female FVB mice were imaged with a 4.7-T MR scanner using both 2D and high resolution 3D sequences. Inner ear region of interest (ROI) signal intensities and perilymph volumes were evaluated. Finer structures were studied using 3D acquisition and reconstruction techniques and comparisons were made to similarly oriented histological sections that were examined by light microscopy. Gd-DOTA enhancement occurred in the perilymphatic compartment and highlighted the contiguous inner ear structures, but enhancement did not appear within the endolymph. The dynamic uptake of Gd-DOTA in the perilymphatic compartments reached an initial plateau 80min after IV administration and continued to slightly increase to a maximum level by 100min. The perilymph volume demonstrated by Gd-DOTA uptake was statistically significantly larger in the IV group (1.72mm(3)) than in the IT group (1.28mm(3)) (p<0.05).

  18. Hemispheric asymmetry in cerebrovascular reactivity of the human primary motor cortex: an in vivo study at 7 T.

    PubMed

    Driver, Ian D; Andoh, Jamila; Blockley, Nicholas P; Francis, Susan T; Gowland, Penny A; Paus, Tomáš

    2015-05-01

    Current functional MRI (fMRI) approaches assess underlying neuronal activity through monitoring the related local variations in cerebral blood oxygenation, blood volume and blood flow. This vascular response is likely to vary across brain regions and across individuals, depending on the composition of the local vascular bed and on the vascular capacity to dilate. The most widely used technique uses the blood oxygen level dependent (BOLD) fMRI signal, which arises from a complex combination of all of these factors. The model of handedness provides a case where one brain region (dominant motor cortex) is known to have a stronger BOLD response over another (non-dominant motor cortex) during hand motor task performance. We predict that this is accompanied by a higher vascular reactivity in the dominant motor cortex, when compared with the non-dominant motor cortex. Precise measurement of end-tidal CO2 and a novel sinusoidal CO2 respiratory challenge were combined with the high sensitivity and finer spatial resolution available for fMRI at 7 T to measure BOLD cerebrovascular reactivity (CVR) in eight healthy male participants. BOLD CVR was compared between the left (dominant) and right (non-dominant) primary motor cortices of right-handed adults. Hemispheric asymmetry in vascular reactivity was predicted and observed in the primary motor cortex (left CVR = 0.60 ± 0.15%/mm Hg; right CVR = 0.47 ± 0.08%/mm Hg; left CVR > right CVR, P = 0.04), the first reported evidence of such a vascular difference. These findings demonstrate a cerebral vascular asymmetry between the left and right primary motor cortex. The origin of this asymmetry largely arises from the contribution of large draining veins. This work has implications for future motor laterality studies that use BOLD, and it is also suggestive of a vascular plasticity in the human primary motor cortex. PMID:25788020

  19. Detection of lactate in the striatum without contamination of macromolecules by J-difference editing MRS at 7T.

    PubMed

    Wijnen, J P; Haarsma, J; Boer, V O; Luijten, P R; van der Stigchel, S; Neggers, S F W; Klomp, D W J

    2015-04-01

    Lactate levels are measurable by MRS and are related to neural activity. Therefore, it is of interest to accurately measure lactate levels in the basal ganglia networks. If sufficiently stable, lactate measurements may be used to investigate alterations in dopaminergic signalling in the striatum, facilitating the detection and diagnosis of metabolic deficits. The aim of this study is to provide a J-difference editing MRS technique for the selective editing of lactate only, thus allowing the detection of lactate without contamination of overlapping macromolecules. As a validation procedure, macromolecule nulling was combined with J-difference editing, and this was compared with J-difference editing with a new highly selective editing pulse. The use of a high-field (7T) MR scanner enables the application of editing pulses with very narrow bandwidth, which are selective for lactate. We show that, despite the sensitivity to B0 offsets, the use of a highly selective editing pulse is more efficient for the detection of lactate than the combination of a broad-band editing pulse with macromolecule nulling. Although the signal-to-noise ratio of uncontaminated lactate detection in healthy subjects is relatively low, this article describes the test-retest performance of lactate detection in the striatum when using highly selective J-difference editing MRS at 7 T. The coefficient of variation, σw and intraclass correlation coefficients for within- and between-subject differences of lactate were determined. Lactate levels in the left and right striatum were determined twice in 10 healthy volunteers. Despite the fact that the test-retest performance of lactate detection is moderate with a coefficient of variation of about 20% for lactate, these values can be used for the design of new studies comparing, for example, patient populations with healthy controls.

  20. Assessment of human hippocampal developmental neuroanatomy by means of ex-vivo 7 T magnetic resonance imaging.

    PubMed

    Milesi, Gloria; Garbelli, Rita; Zucca, Ileana; Aronica, Eleonora; Spreafico, Roberto; Frassoni, Carolina

    2014-05-01

    During development, the hippocampus undergoes numerous changes in its cell morphology and cyto- and myelo-architecture that begin during the fetal period and continue after birth. We investigated the developmental changes occurring in healthy fetal (20-32 gestational weeks) and post-natal human hippocampi (from 1 day to adulthood) by combining high-resolution 7 T magnetic resonance imaging (MRI) and histological and immunohistochemical analyses in order to compare variations in signal intensity with cyto- and myeloarchitectural organization. During fetal period the intensity of the T2-weighted images was related to the cell density and the subregions of Ammon's horn and dentate gyrus, characterized by densely packed neurons, were recognizable as hypointense areas. The inverse correlation between MRI signal intensity and cell density was visualized by line profile results. At the age of two post-natal weeks, the low MRI signal was still related to cell density, although thin myelinated fibers were observed in hypointense regions such as the alveus and stratum lacunosum-moleculare. The myelin content subsequently increases until the complete hippocampal myeloarchitecture is reached in adulthood. Comparison of the MRI findings and corresponding histological sections indicated that the differences in the T2-weighted images between the age of seven years and adulthood reflect the increasing density of myelinated fibers. These results provide useful information concerning the interpretation of MRI signals and the developmental changes visualized by in vivo MRI at lower field strengths, and may be used as a reference for the future use of high spatial resolution MRI in clinical practice.

  1. Segmentation of perivascular spaces in 7T MR image using auto-context model with orientation-normalized features.

    PubMed

    Park, Sang Hyun; Zong, Xiaopeng; Gao, Yaozong; Lin, Weili; Shen, Dinggang

    2016-07-01

    Quantitative study of perivascular spaces (PVSs) in brain magnetic resonance (MR) images is important for understanding the brain lymphatic system and its relationship with neurological diseases. One of the major challenges is the accurate extraction of PVSs that have very thin tubular structures with various directions in three-dimensional (3D) MR images. In this paper, we propose a learning-based PVS segmentation method to address this challenge. Specifically, we first determine a region of interest (ROI) by using the anatomical brain structure and the vesselness information derived from eigenvalues of image derivatives. Then, in the ROI, we extract a number of randomized Haar features which are normalized with respect to the principal directions of the underlying image derivatives. The classifier is trained by the random forest model that can effectively learn both discriminative features and classifier parameters to maximize the information gain. Finally, a sequential learning strategy is used to further enforce various contextual patterns around the thin tubular structures into the classifier. For evaluation, we apply our proposed method to the 7T brain MR images scanned from 17 healthy subjects aged from 25 to 37. The performance is measured by voxel-wise segmentation accuracy, cluster-wise classification accuracy, and similarity of geometric properties, such as volume, length, and diameter distributions between the predicted and the true PVSs. Moreover, the accuracies are also evaluated on the simulation images with motion artifacts and lacunes to demonstrate the potential of our method in segmenting PVSs from elderly and patient populations. The experimental results show that our proposed method outperforms all existing PVS segmentation methods. PMID:27046107

  2. A multi-channel biomimetic neuroprosthesis to support treadmill gait training in stroke patients.

    PubMed

    Chia, Noelia; Ambrosini, Emilia; Baccinelli, Walter; Nardone, Antonio; Monticone, Marco; Ferrigno, Giancarlo; Pedrocchi, Alessandra; Ferrante, Simona

    2015-01-01

    This study presents an innovative multi-channel neuroprosthesis that induces a biomimetic activation of the main lower-limb muscles during treadmill gait training to be used in the rehabilitation of stroke patients. The electrostimulation strategy replicates the physiological muscle synergies used by healthy subjects to walk on a treadmill at their self-selected speed. This strategy is mapped to the current gait sub-phases, which are identified in real time by a custom algorithm. This algorithm divides the gait cycle into six sub-phases, based on two inertial sensors placed laterally on the shanks. Therefore, the pre-defined stimulation profiles are expanded or stretched based on the actual gait pattern of each single subject. A preliminary experimental protocol, involving 10 healthy volunteers, was carried out to extract the muscle synergies and validate the gait-detection algorithm, which were afterwards used in the development of the neuroprosthesis. The feasibility of the neuroprosthesis was tested on one healthy subject who simulated different gait patterns, and a chronic stroke patient. The results showed the correct functioning of the system. A pilot study of the neurorehabilitation treatment for stroke patients is currently being carried out.

  3. Hyperbolic Positioning with Antenna Arrays and Multi-Channel Pseudolite for Indoor Localization

    PubMed Central

    Fujii, Kenjirou; Sakamoto, Yoshihiro; Wang, Wei; Arie, Hiroaki; Schmitz, Alexander; Sugano, Shigeki

    2015-01-01

    A hyperbolic positioning method with antenna arrays consisting of proximately-located antennas and a multi-channel pseudolite is proposed in order to overcome the problems of indoor positioning with conventional pseudolites (ground-based GPS transmitters). A two-dimensional positioning experiment using actual devices is conducted. The experimental result shows that the positioning accuracy varies centimeter- to meter-level according to the geometric relation between the pseudolite antennas and the receiver. It also shows that the bias error of the carrier-phase difference observables is more serious than their random error. Based on the size of the bias error of carrier-phase difference that is inverse-calculated from the experimental result, three-dimensional positioning performance is evaluated by computer simulation. In addition, in the three-dimensional positioning scenario, an initial value convergence analysis of the non-linear least squares is conducted. Its result shows that initial values that can converge to a right position exist at least under the proposed antenna setup. The simulated values and evaluation methods introduced in this work can be applied to various antenna setups; therefore, by using them, positioning performance can be predicted in advance of installing an actual system. PMID:26437405

  4. 26 CFR 1.897-7T - Treatment of certain partnership interests as entirely U.S. real property interests under...

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... entirely U.S. real property interests under sections 897(g) and 1445(e) (temporary). 1.897-7T Section 1.897... entirely U.S. real property interests under sections 897(g) and 1445(e) (temporary). (a) Rule. Pursuant to... the value of the gross assets consist of U.S. real property interests, and ninety percent or more...

  5. 26 CFR 20.2031-7T - Valuation of annuities, interests for life or term of years, and remainder or reversionary...

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... ESTATE TAX; ESTATES OF DECEDENTS DYING AFTER AUGUST 16, 1954 Gross Estate § 20.2031-7T Valuation of... section 7520 rate for the month in which the decedent died is 5.6 percent. Under Table S in paragraph (d... and 5 months old. In the month in which the decedent died, the section 7520 rate was 6.2...

  6. 26 CFR 20.2031-7T - Valuation of annuities, interests for life or term of years, and remainder or reversionary...

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... ESTATE TAX; ESTATES OF DECEDENTS DYING AFTER AUGUST 16, 1954 Gross Estate § 20.2031-7T Valuation of... section 7520 rate for the month in which the decedent died is 5.6 percent. Under Table S in paragraph (d... and 5 months old. In the month in which the decedent died, the section 7520 rate was 6.2...

  7. 26 CFR 1.897-7T - Treatment of certain partnership interests as entirely U.S. real property interests under...

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... entirely U.S. real property interests under sections 897(g) and 1445(e) (temporary). 1.897-7T Section 1.897... interests as entirely U.S. real property interests under sections 897(g) and 1445(e) (temporary). (a) Rule... more of the value of the gross assets consist of U.S. real property interests, and ninety percent...

  8. 26 CFR 1.897-7T - Treatment of certain partnership interests as entirely U.S. real property interests under...

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... entirely U.S. real property interests under sections 897(g) and 1445(e) (temporary). 1.897-7T Section 1.897... interests as entirely U.S. real property interests under sections 897(g) and 1445(e) (temporary). (a) Rule... more of the value of the gross assets consist of U.S. real property interests, and ninety percent...

  9. On multichannel film dosimetry with channel-independent perturbations

    SciTech Connect

    Méndez, I. Peterlin, P.; Hudej, R.; Strojnik, A.; Casar, B.

    2014-01-15

    Purpose: Different multichannel methods for film dosimetry have been proposed in the literature. Two of them are the weighted mean method and the method put forth byMicke et al. [“Multichannel film dosimetry with nonuniformity correction,” Med. Phys. 38, 2523–2534 (2011)] and Mayer et al. [“Enhanced dosimetry procedures and assessment for EBT2 radiochromic film,” Med. Phys. 39, 2147–2155 (2012)]. The purpose of this work was to compare their results and to develop a generalized channel-independent perturbations framework in which both methods enter as special cases. Methods: Four models of channel-independent perturbations were compared: weighted mean, Micke–Mayer method, uniform distribution, and truncated normal distribution. A closed-form formula to calculate film doses and the associated type B uncertainty for all four models was deduced. To evaluate the models, film dose distributions were compared with planned and measured dose distributions. At the same time, several elements of the dosimetry process were compared: film type EBT2 versus EBT3, different waiting-time windows, reflection mode versus transmission mode scanning, and planned versus measured dose distribution for film calibration and for γ-index analysis. The methods and the models described in this study are publicly accessible through IRISEU. Alpha 1.1 ( http://www.iriseu.com ). IRISEU. is a cloud computing web application for calibration and dosimetry of radiochromic films. Results: The truncated normal distribution model provided the best agreement between film and reference doses, both for calibration and γ-index verification, and proved itself superior to both the weighted mean model, which neglects correlations between the channels, and the Micke–Mayer model, whose accuracy depends on the properties of the sensitometric curves. With respect to the selection of dosimetry protocol, no significant differences were found between transmission and reflection mode scanning

  10. Multichannel Microwave Interferometer for Simultaneous Measurement of Electron Density and its Fluctuation on HL-2A Tokamak

    NASA Astrophysics Data System (ADS)

    Shi, Peiwan; Shi, Zhongbing; Chen, Wei; Zhong, Wulyu; Yang, Zengchen; Jiang, Min; Zhang, Boyu; Li, Yonggao; Yu, Liming; Liu, Zetian; Ding, Xuantong

    2016-07-01

    A multichannel microwave interferometer system has been developed on the HL-2A tokomak. Its working frequency is well designed to avoid the fringe jump effect. Taking the structure of HL-2A into account, its antennas are installed in the horizontal direction, i.e. one launcher in high field side (HFS) and four receivers in low field side (LFS). The fan-shaped measurement area covers those regions where the magnetohydrodynamics (MHD) instabilities are active. The heterodyne technique contributes to its high temporal resolution (1 μs). It is possible for the multichannel system to realize simultaneous measurements of density and its fluctuation. The quadrature phase detection based on the zero-crossing method is introduced to density measurement. With this system, reliable line-averaged densities and density profiles are obtained. The location of the saturated internal kink mode can be figured out from the mode showing different intensities on four channels, and the result agrees well with that measured by electron cyclotron emission imaging (ECEI). supported by the National Magnetic Confinement Fusion Science Program of China (Nos. 2013GB104002, 2013GB107002, 2014GB107001) and National Natural Science Foundation of China (Nos. 11475058, 11475057, 11261140326, 11405049)

  11. Improving Pulse Rate Measurements during Random Motion Using a Wearable Multichannel Reflectance Photoplethysmograph.

    PubMed

    Warren, Kristen M; Harvey, Joshua R; Chon, Ki H; Mendelson, Yitzhak

    2016-01-01

    Photoplethysmographic (PPG) waveforms are used to acquire pulse rate (PR) measurements from pulsatile arterial blood volume. PPG waveforms are highly susceptible to motion artifacts (MA), limiting the implementation of PR measurements in mobile physiological monitoring devices. Previous studies have shown that multichannel photoplethysmograms can successfully acquire diverse signal information during simple, repetitive motion, leading to differences in motion tolerance across channels. In this paper, we investigate the performance of a custom-built multichannel forehead-mounted photoplethysmographic sensor under a variety of intense motion artifacts. We introduce an advanced multichannel template-matching algorithm that chooses the channel with the least motion artifact to calculate PR for each time instant. We show that for a wide variety of random motion, channels respond differently to motion artifacts, and the multichannel estimate outperforms single-channel estimates in terms of motion tolerance, signal quality, and PR errors. We have acquired 31 data sets consisting of PPG waveforms corrupted by random motion and show that the accuracy of PR measurements achieved was increased by up to 2.7 bpm when the multichannel-switching algorithm was compared to individual channels. The percentage of PR measurements with error ≤ 5 bpm during motion increased by 18.9% when the multichannel switching algorithm was compared to the mean PR from all channels. Moreover, our algorithm enables automatic selection of the best signal fidelity channel at each time point among the multichannel PPG data. PMID:26959034

  12. Improving Pulse Rate Measurements during Random Motion Using a Wearable Multichannel Reflectance Photoplethysmograph

    PubMed Central

    Warren, Kristen M.; Harvey, Joshua R.; Chon, Ki H.; Mendelson, Yitzhak

    2016-01-01

    Photoplethysmographic (PPG) waveforms are used to acquire pulse rate (PR) measurements from pulsatile arterial blood volume. PPG waveforms are highly susceptible to motion artifacts (MA), limiting the implementation of PR measurements in mobile physiological monitoring devices. Previous studies have shown that multichannel photoplethysmograms can successfully acquire diverse signal information during simple, repetitive motion, leading to differences in motion tolerance across channels. In this paper, we investigate the performance of a custom-built multichannel forehead-mounted photoplethysmographic sensor under a variety of intense motion artifacts. We introduce an advanced multichannel template-matching algorithm that chooses the channel with the least motion artifact to calculate PR for each time instant. We show that for a wide variety of random motion, channels respond differently to motion artifacts, and the multichannel estimate outperforms single-channel estimates in terms of motion tolerance, signal quality, and PR errors. We have acquired 31 data sets consisting of PPG waveforms corrupted by random motion and show that the accuracy of PR measurements achieved was increased by up to 2.7 bpm when the multichannel-switching algorithm was compared to individual channels. The percentage of PR measurements with error ≤ 5 bpm during motion increased by 18.9% when the multichannel switching algorithm was compared to the mean PR from all channels. Moreover, our algorithm enables automatic selection of the best signal fidelity channel at each time point among the multichannel PPG data. PMID:26959034

  13. Assessment of blood flow velocity and pulsatility in cerebral perforating arteries with 7-T quantitative flow MRI.

    PubMed

    Bouvy, W H; Geurts, L J; Kuijf, H J; Luijten, P R; Kappelle, L J; Biessels, G J; Zwanenburg, J J M

    2016-09-01

    Thus far, blood flow velocity measurements with MRI have only been feasible in large cerebral blood vessels. High-field-strength MRI may now permit velocity measurements in much smaller arteries. The aim of this proof of principle study was to measure the blood flow velocity and pulsatility of cerebral perforating arteries with 7-T MRI. A two-dimensional (2D), single-slice quantitative flow (Qflow) sequence was used to measure blood flow velocities during the cardiac cycle in perforating arteries in the basal ganglia (BG) and semioval centre (CSO), from which a mean normalised pulsatility index (PI) per region was calculated (n = 6 human subjects, aged 23-29 years). The precision of the measurements was determined by repeated imaging and performance of a Bland-Altman analysis, and confounding effects of partial volume and noise on the measurements were simulated. The median number of arteries included was 14 in CSO and 19 in BG. In CSO, the average velocity per volunteer was in the range 0.5-1.0 cm/s and PI was 0.24-0.39. In BG, the average velocity was in the range 3.9-5.1 cm/s and PI was 0.51-0.62. Between repeated scans, the precision of the average, maximum and minimum velocity per vessel decreased with the size of the arteries, and was relatively low in CSO and BG compared with the M1 segment of the middle cerebral artery. The precision of PI per region was comparable with that of M1. The simulations proved that velocities can be measured in vessels with a diameter of more than 80 µm, but are underestimated as a result of partial volume effects, whilst pulsatility is overestimated. Blood flow velocity and pulsatility in cerebral perforating arteries have been measured directly in vivo for the first time, with moderate to good precision. This may be an interesting metric for the study of haemodynamic changes in aging and cerebral small vessel disease. © 2015 The Authors NMR in Biomedicine Published by John Wiley & Sons Ltd.

  14. Multi-channel OLA Inversion for Local Helioseismology

    NASA Astrophysics Data System (ADS)

    Jackiewicz, Jason; Birch, A.; Gizon, L.

    2009-05-01

    We present preliminary results of a three-dimensional inversion for local helioseismology, in particular utilizing the time-distance technique. This inversion is unique in that in combines a Fourier-space multi-channel deconvolution with the optimally localized averages (OLA) method. The result is a very computationally efficient procedure that is fully parallelizable and suited for large-scale inversions needed for future studies. A simple example of the inversion is shown using point-to-point Born approximation kernels for sound-speed perturbations and the travel-time noise covariance. A step-by-step comparison is shown with a recently developed real-space OLA inversion to demonstrate the benefits of a Fourier-space formulation.

  15. A calibration method of the multi-channel imaging lidar

    NASA Astrophysics Data System (ADS)

    Xu, Weiming; Liu, Jun; Shu, Rong

    2014-06-01

    We design a kind of imaging LiDAR with sixteen channels, which consists of a fiber laser source, dual scanning galvanometers, range measurement circuits and information processing circuits etc. The image LiDAR provides sixteen range measurements for one laser shot and the distance accuracy of each channel is about 4cm. This paper provides a calibrate method to correct point cloud images captured with the multi-channel LiDAR. The method needs to construct different slanted planes to cover the imaging field, and establish precise plane equations in the known ground coordinates, then fit planes with point clouds data and calculate correction parameters of all channels through the error model. The image accuracy is better than 5cm processed by this calibration method.

  16. A study of fault injection in multichannel spacecraft power systems

    NASA Technical Reports Server (NTRS)

    Dugal-Whitehead, Norma R.; Johnson, Yvette B.

    1991-01-01

    NASA/Marshall Space Flight Center proposes to implement fault injection into an electrical power system breadboard to study the reactions of the various control elements of this breadboard. Among the elements to be studied are the remote power controllers, the algorithms in the control computers, and the artificially intelligent control programs resident in this breadboard. To this end, a study of electrical power is being performed to yield a list of the most common power system faults. The results of this study are being applied to a multichannel high-voltage DC spacecraft power system called the Large Autonomous Spacecraft Electrical Power System Breadboard. Some of the reactions of the breadboard to some of the faults which have been encountered are presented along with the results of this study.

  17. Multichannel quantum defect theory of photodissociation in H2

    NASA Astrophysics Data System (ADS)

    Mezei, J. Zs.; Schneider, I. F.; Jungen, Ch.

    2015-01-01

    The predissociation profiles of the R(0), R(1) and R(2) lines of the 3pπ1Πu+,v = 3 ←X1Σg+,v'' = 0 absorption transition in H2 are calculated in a multichannel quantum defect theory approach, implemented on the basis of state-of-the-art potential energy curves (PEC) from the Wolniewicz group. It is shown that the profiles may be very accurately represented by the Fano profile formula although the resonance parameters thus determined do not exactly coincide with the meaning given to them in Fano's original derivation. The recent high-resolution spectrum of the same transitions taken with the SOLEIL synchrotron is well reproduced by the calculations.

  18. Automated distribution system management for multichannel space power systems

    NASA Technical Reports Server (NTRS)

    Fleck, G. W.; Decker, D. K.; Graves, J.

    1983-01-01

    A NASA sponsored study of space power distribution system technology is in progress to develop an autonomously managed power system (AMPS) for large space power platforms. The multichannel, multikilowatt, utility-type power subsystem proposed presents new survivability requirements and increased subsystem complexity. The computer controls under development for the power management system must optimize the power subsystem performance and minimize the life cycle cost of the platform. A distribution system management philosophy has been formulated which incorporates these constraints. Its implementation using a TI9900 microprocessor and FORTH as the programming language is presented. The approach offers a novel solution to the perplexing problem of determining the optimal combination of loads which should be connected to each power channel for a versatile electrical distribution concept.

  19. Performance prediction for 3D filtering of multichannel images

    NASA Astrophysics Data System (ADS)

    Rubel, Oleksii; Kozhemiakin, Ruslan A.; Abramov, Sergey K.; Lukin, Vladimir V.; Vozel, Benoit; Chehdi, Kacem

    2015-10-01

    Performance of denoising based on discrete cosine transform applied to multichannel remote sensing images corrupted by additive white Gaussian noise is analyzed. Images obtained by satellite Earth Observing-1 (EO-1) mission using hyperspectral imager instrument (Hyperion) that have high input SNR are taken as test images. Denoising performance is characterized by improvement of PSNR. For hard-thresholding 3D DCT-based denoising, simple statistics (probabilities to be less than a certain threshold) are used to predict denoising efficiency using curves fitted into scatterplots. It is shown that the obtained curves (approximations) provide prediction of denoising efficiency with high accuracy. Analysis is carried out for different numbers of channels processed jointly. Universality of prediction for different number of channels is proven.

  20. Multichannel DC SQUID sensor array for biomagnetic applications

    SciTech Connect

    Hoenig, H.E.; Daalmans, G.M.; Bar, L.; Bommel, F.; Paulus, A.; Uhl, D.; Weisse, H.J. ); Schneider, S.; Seifert, H.; Reichenberger, H.; Abraham-Fuchs, K. )

    1991-03-01

    This paper reports on a biomagnetic multichannel system for medical diagnosis of brain and heart KRENIKON has been developed. 37 axial 2st order gradiometers - manufactured as flexible superconducting printed circuits - are arranged in a circular flat array of 19 cm diameter. Additionally, 3 orthogonal magnetometers are provided. The DC SQUIDs are fabricated in all-Nb technology, ten on a chip. The sensor system is operated in a shielded room with two layers of soft magnetic material and one layer of Al. The every day noise level is 10 fT/Hz{sup 1/2} at frequencies above 10 Hz. Within 2 years of operation in a normal urban surrounding, useful clinical applications have been demonstrated (e.g. for epilepsy and heart arrhythmias).

  1. Experience with a multichannel system for biomagnetic study.

    PubMed

    Schneider, S; Abraham-Fuchs, K; Reichenberger, H; Seifert, H; Hoenig, H E; Röhrlein, G

    1993-11-01

    The components of the biomagnetic multichannel system Krenikon are described. The combination of biomagnetically yielded localizations with anatomic images gained from MR or CT is discussed as well as the enhancement of the signal-to-noise ratio by using a correlation technique. The overall localization accuracy is tested with technical phantoms. With volunteers measurements of auditory, visual and somatosensory evoked fields are performed to evaluate the system performance in vivo. Clinical studies were performed mainly with partners from the Universities of Erlangen-Nünberg and Ulm. The data acquisition time typically is 2-10 min which is tolerable both for the patient and the clinical staff. Electric potentials even with invasive electrodes can be recorded simultaneously with the magnetic fields. MEG gives important information for the presurgical diagnosis of epileptic patients and for the understanding of the epilepsy genesis. With MCG, centres of biologic excitation such as ventricular ectopies or accessory bundles in WPW syndrome have been successfully localized.

  2. Multichannel quantum defect theory for cold molecular collisions

    SciTech Connect

    Croft, James F. E.; Wallis, Alisdair O. G.; Hutson, Jeremy M.; Julienne, Paul S.

    2011-10-15

    Multichannel quantum defect theory (MQDT) is shown to be capable of producing quantitatively accurate results for low-energy atom-molecule scattering calculations. With a suitable choice of reference potential and short-range matching distance, it is possible to define a matrix that encapsulates the short-range collision dynamics and is only weakly dependent on energy and magnetic field. Once this has been produced, calculations at additional energies and fields can be performed at a computational cost that is proportional to the number of channels N and not to N{sup 3}. MQDT thus provides a promising method for carrying out low-energy molecular scattering calculations on systems where full exploration of the energy dependence and the field dependence is currently impractical.

  3. Electronic systems for the new multichannel spectrometer at Sacramento Peak.

    NASA Technical Reports Server (NTRS)

    Hobbs, R. W.; Harris, G. D.; Epstein, G.

    1972-01-01

    Description of the design features and operation of a new multichannel solar spectrometer to be used for ground-based observations of active regions whose X-ray and EUV emissions are studied by the OSO-H and other satellites. The electronic systems associated with the instrument include (1) an electrooptical guider controlled by a punched paper tape capable of making raster scans of selected portions of the solar disk, (2) a programmer unit that applies paper-tape commands to various portions of the instrument, (3) a closed-loop servosystem for the vacuum heliostat, (4) stepping motor controls for spectral scans, (5) a 40-channel photomultiplier readout, and (6) a magnetometer. Preliminary solar observations indicate satisfactory performance of the system.

  4. A multichannel nanosensor for instantaneous readout of cancer drug mechanisms

    NASA Astrophysics Data System (ADS)

    Rana, Subinoy; Le, Ngoc D. B.; Mout, Rubul; Saha, Krishnendu; Tonga, Gulen Yesilbag; Bain, Robert E. S.; Miranda, Oscar R.; Rotello, Caren M.; Rotello, Vincent M.

    2015-01-01

    Screening methods that use traditional genomic, transcriptional, proteomic and metabonomic signatures to characterize drug mechanisms are known. However, they are time consuming and require specialized equipment. Here, we present a high-throughput multichannel sensor platform that can profile the mechanisms of various chemotherapeutic drugs in minutes. The sensor consists of a gold nanoparticle complexed with three different fluorescent proteins that can sense drug-induced physicochemical changes on cell surfaces. In the presence of cells, fluorescent proteins are rapidly displaced from the gold nanoparticle surface and fluorescence is restored. Fluorescence ‘turn on’ of the fluorescent proteins depends on the drug-induced cell surface changes, generating patterns that identify specific mechanisms of cell death induced by drugs. The nanosensor is generalizable to different cell types and does not require processing steps before analysis, offering an effective way to expedite research in drug discovery, toxicology and cell-based sensing.

  5. Tunable multi-channel terahertz wave power splitter

    NASA Astrophysics Data System (ADS)

    Jiu-Sheng, Li; Han, Liu; Le, Zhang

    2015-12-01

    The combination of terahertz technology and photonic crystal provides a new approach to realize compact terahertz wave devices. Relying on a conventional photonic crystal waveguide and photonic crystal surface-mode waveguides, a tunable multi-channel terahertz-wave power splitter is proposed. The mechanism of such a power splitter is further theoretically analyzed and numerically investigated with the aid of the plane-wave-expansion method and the finite-difference time-domain method. With an appropriate design, the proposed device can split the input terahertz wave energy equally into six output ports at the frequency of 0.6 THz. When changing the external magnetic field, the input terahertz wave can be equally divided into four output ports with the aid of a magnetic-sensitive material. Furthermore, the present device is very compact and the total size is of 4.4×6.0 mm2.

  6. Large capacity, high-speed multiparameter multichannel analysis system

    SciTech Connect

    Hendricks, R.W.; Seeger, P.A.; Scheer, J.W.; Suehiro, S.

    1980-01-01

    A data acquisition system for recording multiparameter digital data into a large memory array at over 2.5 MHz is described. The system consists of a MOSTEK MK8600 2048K x 24-bit memory system, I/O ports to various external devices including the CAMAC dataway, a memory incrementer/adder and a daisy-chain of experiment-specific modules which calculate the memory address which is to be incremented. The design of the daisy-chain permits multiple modules and provides for easy modification as experimental needs change. The system has been designed for use in multiparameter, multichannel analysis of high-speed data gathered by position-sensitive detectors at conventional and synchrotron x-ray sources as well as for fixed energy and time-of-flight diffraction at continuous and pulsed neutron sources.

  7. Multi-channel detector readout method and integrated circuit

    DOEpatents

    Moses, William W.; Beuville, Eric; Pedrali-Noy, Marzio

    2004-05-18

    An integrated circuit which provides multi-channel detector readout from a detector array. The circuit receives multiple signals from the elements of a detector array and compares the sampled amplitudes of these signals against a noise-floor threshold and against one another. A digital signal is generated which corresponds to the location of the highest of these signal amplitudes which exceeds the noise floor threshold. The digital signal is received by a multiplexing circuit which outputs an analog signal corresponding the highest of the input signal amplitudes. In addition a digital control section provides for programmatic control of the multiplexer circuit, amplifier gain, amplifier reset, masking selection, and test circuit functionality on each input thereof.

  8. Multi-channel detector readout method and integrated circuit

    DOEpatents

    Moses, William W.; Beuville, Eric; Pedrali-Noy, Marzio

    2006-12-12

    An integrated circuit which provides multi-channel detector readout from a detector array. The circuit receives multiple signals from the elements of a detector array and compares the sampled amplitudes of these signals against a noise-floor threshold and against one another. A digital signal is generated which corresponds to the location of the highest of these signal amplitudes which exceeds the noise floor threshold. The digital signal is received by a multiplexing circuit which outputs an analog signal corresponding the highest of the input signal amplitudes. In addition a digital control section provides for programmatic control of the multiplexer circuit, amplifier gain, amplifier reset, masking selection, and test circuit functionality on each input thereof.

  9. Instrumentation considerations in multichannel ellipsometry for real-time spectroscopy

    NASA Astrophysics Data System (ADS)

    An, Ilsin; Cong, Yue; Nguyen, N. V.; Pudliner, B. S.; Collins, R. W.

    Experimental procedures are described to enhance the accuracy of a novel rotating polarizer multichannel ellipsometer, designed for real-time spectroscopic studies of film growth and surfaces. For the fastest such instrument 128-point (psi, delta) spectra from 1.5 to 4.5 eV can be acquired in less than 10 ms. Ellipsometry places stringent demands on the photodiode-array-based detection system, as the irradiance incident on the separate pixels is waveform analyzed. A detailed characterization of the detection system is presented which provides the means to correct for stray light, image persistence, non-linearity, and integration errors. We also outline techniques for characterization of imperfection associated with the source and polarization optics. We present calibration and data reduction equations which have been derived to include source and polarization system imperfection parameters to first order.

  10. Multichannel Brain-Signal-Amplifying and Digitizing System

    NASA Technical Reports Server (NTRS)

    Gevins, Alan

    2005-01-01

    An apparatus has been developed for use in acquiring multichannel electroencephalographic (EEG) data from a human subject. EEG apparatuses with many channels in use heretofore have been too heavy and bulky to be worn, and have been limited in dynamic range to no more than 18 bits. The present apparatus is small and light enough to be worn by the subject. It is capable of amplifying EEG signals and digitizing them to 22 bits in as many as 150 channels. The apparatus is controlled by software and is plugged into the USB port of a personal computer. This apparatus makes it possible, for the first time, to obtain high-resolution functional EEG images of a thinking brain in a real-life, ambulatory setting outside a research laboratory or hospital.

  11. Fast Stimulus Artifact Recovery in a Multichannel Neural Recording System

    PubMed Central

    Schoenecker, Matthew C.; Bonham, Ben H.

    2010-01-01

    We describe a 32-channel recording system and software artifact blanking technique for recording neuronal responses to high-rate electrical stimulation. Each recording channel recovers from biphasic full-scale-input pulses (1.5-V) in less than 80 μs. Artifacts are blanked online in software, allowing flexibility in the choice of blanking period and the possibility of recovering neural data occurring simultaneously with non-saturating artifacts. The system has been used in-vivo to record central neuronal responses to intracochlear electrical stimulation at 2000 pulses per second. Simplicity of the hardware design makes the technique well suited to an implantable multi-channel recording system. PMID:20559458

  12. Automatic landslide and mudflow detection method via multichannel sparse representation

    NASA Astrophysics Data System (ADS)

    Chao, Chen; Zhou, Jianjun; Hao, Zhuo; Sun, Bo; He, Jun; Ge, Fengxiang

    2015-10-01

    Landslide and mudflow detection is an important application of aerial images and high resolution remote sensing images, which is crucial for national security and disaster relief. Since the high resolution images are often large in size, it's necessary to develop an efficient algorithm for landslide and mudflow detection. Based on the theory of sparse representation and, we propose a novel automatic landslide and mudflow detection method in this paper, which combines multi-channel sparse representation and eight neighbor judgment methods. The whole process of the detection is totally automatic. We make the experiment on a high resolution image of ZhouQu district of Gansu province in China on August, 2010 and get a promising result which proved the effective of using sparse representation on landslide and mudflow detection.

  13. A scalable correlator for multichannel diffuse correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Stapels, Christopher J.; Kolodziejski, Noah J.; McAdams, Daniel; Podolsky, Matthew J.; Fernandez, Daniel E.; Farkas, Dana; Christian, James F.

    2016-03-01

    Diffuse correlation spectroscopy (DCS) is a technique which enables powerful and robust non-invasive optical studies of tissue micro-circulation and vascular blood flow. The technique amounts to autocorrelation analysis of coherent photons after their migration through moving scatterers and subsequent collection by single-mode optical fibers. A primary cost driver of DCS instruments are the commercial hardware-based correlators, limiting the proliferation of multi-channel instruments for validation of perfusion analysis as a clinical diagnostic metric. We present the development of a low-cost scalable correlator enabled by microchip-based time-tagging, and a software-based multi-tau data analysis method. We will discuss the capabilities of the instrument as well as the implementation and validation of 2- and 8-channel systems built for live animal and pre-clinical settings.

  14. Detection of forced oscillations in power systems with multichannel methods

    SciTech Connect

    Follum, James D.

    2015-09-30

    The increasing availability of high fidelity, geographically dispersed measurements in power systems improves the ability of researchers and engineers to study dynamic behaviors in the grid. One such behavior that is garnering increased attention is the presence of forced oscillations. Power system engineers are interested in forced oscillations because they are often symptomatic of the malfunction or misoperation of equipment. Though the resulting oscillation is not always large in amplitude, the root cause may be serious. In this report, multi-channel forced oscillation detection methods are developed. These methods leverage previously developed detection approaches based on the periodogram and spectral-coherence. Making use of geographically distributed channels of data is shown to improved detection performance and shorten the delay before an oscillation can be detected in the online environment. Results from simulated and measured power system data are presented.

  15. Large-memory real-time multichannel multiplexed pattern recognition

    NASA Technical Reports Server (NTRS)

    Gregory, D. A.; Liu, H. K.

    1984-01-01

    The principle and experimental design of a real-time multichannel multiplexed optical pattern recognition system via use of a 25-focus dichromated gelatin holographic lens (hololens) are described. Each of the 25 foci of the hololens may have a storage and matched filtering capability approaching that of a single-lens correlator. If the space-bandwidth product of an input image is limited, as is true in most practical cases, the 25-focus hololens system has 25 times the capability of a single lens. Experimental results have shown that the interfilter noise is not serious. The system has already demonstrated the storage and recognition of over 70 matched filters - which is a larger capacity than any optical pattern recognition system reported to date.

  16. Multichannel Langmuir probe for turbulence study in Heliotron J.

    PubMed

    Ohshima, S; Yamamoto, S; Takeuchi, M; Nagasaki, K; Mizuuchi, T; Okada, H; Minami, T; Kobayashi, S; Hanatani, K; Konoshima, S; Sano, F

    2010-10-01

    New multichannel Langmuir probe system was developed and installed to Heliotron J. The objective of the new probe is to characterize basic turbulence property and the resulting transport in advanced helical configuration. The probe developed here consists of four sets of triple probe and one pin for floating potential measurement. Initial experiments in neutral beam heating plasma were conducted and fluctuation profile of radial and poloidal electric fields and Reynolds stress were estimated. For precise evaluation of the electric fields and Reynolds stress, a technique to compensate radial change of tilt angle between probe array and magnetic surface was proposed and applied to the initial results obtained in edge region of Heliotron J where the complicated magnetic structure exists.

  17. Multichannel Langmuir probe for turbulence study in Heliotron J

    SciTech Connect

    Ohshima, S.; Yamamoto, S.; Takeuchi, M.; Nagasaki, K.; Mizuuchi, T.; Okada, H.; Minami, T.; Kobayashi, S.; Hanatani, K.; Konoshima, S.; Sano, F.

    2010-10-15

    New multichannel Langmuir probe system was developed and installed to Heliotron J. The objective of the new probe is to characterize basic turbulence property and the resulting transport in advanced helical configuration. The probe developed here consists of four sets of triple probe and one pin for floating potential measurement. Initial experiments in neutral beam heating plasma were conducted and fluctuation profile of radial and poloidal electric fields and Reynolds stress were estimated. For precise evaluation of the electric fields and Reynolds stress, a technique to compensate radial change of tilt angle between probe array and magnetic surface was proposed and applied to the initial results obtained in edge region of Heliotron J where the complicated magnetic structure exists.

  18. The design of a robotic multichannel platform for photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Hu, Yida; Finlay, Jarod C.; Zhu, Timothy C.

    2009-06-01

    A compact robotic platform is designed for simultaneous multichannel motion control for light delivery and dosimetry during interstitial photodynamic therapy (PDT). Movements of light sources and isotropic detectors are controlled by individual motors along different catheters for interstitial PDT. The robotic multichannel platform adds feedback control of positioning for up to 16 channels compared to the existing dual-motor system, which did not have positioning encoders. A 16-channel servo motion controller and micro DC motors, each with high resolution optical encoder, are adopted to control the motions of up to 16 channels independently. Each channel has a resolution of 0.1mm and a speed of 5cm/s. The robotic platform can perform light delivery and dosimetry independently, allowing arbitrary positioning of light sources and detectors in each catheter. Up to 16 compact translational channels can be combined according to different operational scheme with real-time optimal motion planning. The characteristic of high speed and coordinating motion will make it possible to use short linear sources (e.g., 1- cm) to deliver uniform PDT treatment to a bulk tumor within reasonable time by source stepping optimization of multiple sources simultaneously. Advanced robotic control algorithm handles the various unexpected circumstance in clinical procedure, e.g., positiontorque/ current control will be applied to prevent excessive force in the case of resistance in the fiber or motorized mechanism. The robotic platform is fully compatible with operation room (OR) environment and improves the light delivery and dosimetry in PDT. It can be adopted for diffusing optical tomography (DOT), spectroscopic DOT and fluorescent spectroscopy.

  19. Progress in miniaturization of a multichannel optical fiber Bragg grating sensor interrogator

    NASA Astrophysics Data System (ADS)

    Lopatin, Craig M.; Mahmood, Shah; Mendoza, Edgar; Moslehi, Behzad; Black, Richard; Chau, Kelvin; Oblea, Levy

    2007-07-01

    An effort to develop a miniaturized multichannel optical fiber Bragg grating sensor interrogator was initiated in 2006 under the Small Business Innovative Research (SBIR) program. The goal was to develop an interrogator that would be sufficiently small and light to be incorporated into a health monitoring system for use on tactical missiles. Two companies, Intelligent Fiber Optic Systems Corporation (IFOS) and Redondo Optics, were funded in Phase I, and this paper describes the prototype interrogators that were developed. The two companies took very different approaches: IFOS focused on developing a unit that would have a high channel count and high resolution, using off-the-shelf components, while Redondo Optics chose to develop a unit that would be very small and lightweight, using custom designed integrated optical chips. It is believed that both approaches will result in interrogators that will be significantly small, lighter, and possibly even more precise than what is currently commercially available. This paper will also briefly describe some of the sensing concepts that may be used to interrogate the health of the solid rocket motors used in many missile systems. The sponsor of this program was NAVAIR PMA 280.

  20. Multi-channel poloidal correlation reflectometry on experimental advanced superconducting tokamak

    NASA Astrophysics Data System (ADS)

    Qu, H.; Zhang, T.; Han, X.; Xiang, H. M.; Wen, F.; Geng, K. N.; Wang, Y. M.; Kong, D. F.; Cai, J. Q.; Huang, C. B.; Gao, Y.; Gao, X.; Zhang, S.

    2016-11-01

    A new multi-channel poloidal correlation reflectometry is developed at Experimental Advanced Superconducting Tokamak. Eight dielectric resonator oscillators with frequencies of 12.5 GHz, 13.5 GHz, 14.5 GHz, 15 GHz, 15.5 GHz, 16 GHz, 17 GHz, and 18 GHz are used as sources. Signals from the sources are up-converted to V band using active quadruplers and then coupled together. The output waves are launched by one single antenna after passing through a 20 dB directional coupler which can provide the reference signal. Two poloidally separated antennae are installed to receive the reflected waves from plasma. The reference and reflected signals are down-converted by mixing with a quadrupled signal from a phase-locked source with a frequency of 14.2 GHz and the IF signals pass through the filter bank. The resulting signals from the mixers are detected by I/Q demodulators. The setup enables the measurement of density fluctuation at 8 (radial) × 2 (poloidal) spatial points. A coherent mode with an increasing velocity from 50 kHz to 100 kHz is observed by using the system. The mode is located in the steep gradient region of the pedestal.

  1. OCTOCAM: a fast multi-channel imager and spectrograph for the Gemini telescopes

    NASA Astrophysics Data System (ADS)

    de Ugarte Postigo, Antonio

    2015-08-01

    OCTOCAM has been proposed as a future instrument for Gemini and is currently going through a feasibility study phase. Its a multi-channel instrument based on the use of high-efficiency dichroics to divide the light into eight optical and near-infrared arms. In its imaging mode it has a field of view of 3’x3’ that is simultaneously observed in eight bands. It is also designed to obtain spectroscopy from 370 to 2,400 nm in a single shot, with a spectral resolution of ~3,000. OCTOCAM will be capable of obtaining full-Stokes spectropolarimetry to study geometry and magnetic fields of astrophysical phenomena. It will be equipped with a mini-IFU (Integral Field Unit) to perform resolved spectroscopic studies in an area of a few arcseconds. Furthermore, thanks to the use of state of the art detectors, it will be able to reach high readout speeds, allowing science cases aimed at high time-resolution. We expect full frame rate reaching speeds of tens of Hertz, which will be even higher for windowed modes. This will also mean that OCTOCAM will virtually eliminate dead times in most observing modes, allowing duty cycles of roughly 100%. In this way, OCTOCAM will cover a region of the (spectral-resolution)-(spectral-coverage)-(temporal-resolution) diagram that is not occupied by any other single instrument in the world.

  2. Multi-channel linear descriptors for event-related EEG collected in brain computer interface

    NASA Astrophysics Data System (ADS)

    Pei, Xiao-mei; Zheng, Chong-xun; Xu, Jin; Bin, Guang-yu; Wang, Hong-wu

    2006-03-01

    By three multi-channel linear descriptors, i.e. spatial complexity (Ω), field power (Σ) and frequency of field changes (Φ), event-related EEG data within 8-30 Hz were investigated during imagination of left or right hand movement. Studies on the event-related EEG data indicate that a two-channel version of Ω, Σ and Φ could reflect the antagonistic ERD/ERS patterns over contralateral and ipsilateral areas and also characterize different phases of the changing brain states in the event-related paradigm. Based on the selective two-channel linear descriptors, the left and right hand motor imagery tasks are classified to obtain satisfactory results, which testify the validity of the three linear descriptors Ω, Σ and Φ for characterizing event-related EEG. The preliminary results show that Ω, Σ together with Φ have good separability for left and right hand motor imagery tasks, which could be considered for classification of two classes of EEG patterns in the application of brain computer interfaces.

  3. BOLD matches neuronal activity at the mm scale: a combined 7T fMRI and ECoG study in human sensorimotor cortex.

    PubMed

    Siero, Jeroen C W; Hermes, Dora; Hoogduin, Hans; Luijten, Peter R; Ramsey, Nick F; Petridou, Natalia

    2014-11-01

    High resolution BOLD fMRI has the potential to map activation patterns of small neuronal populations at the scale of cortical columns. However, BOLD fMRI does not measure neuronal activity, but only a correlate thereof, since it measures blood dynamics. To confirm that BOLD activation maps reflect neuronal population activity patterns, a direct comparison with neuro-electrophysiological data from the same cortical patch is necessary. Here, we compare BOLD activation patterns obtained with fMRI at 7 T to electrophysiological patterns obtained with implanted high density electrocorticography (ECoG) grids in the same patch of human sensorimotor cortex, and with similar resolution (1.5mm). We used high spatially sampled high-frequency broadband (HFB) power from ECoG, which reflects local neuronal population activity. The spatial distribution of 7 T BOLD activation matched the spatial distribution of ECoG HFB-power changes in the covered patch of sensorimotor cortex. BOLD fMRI activation foci were located within 1-3mm of the HFB-power ECoG foci. Both methods distinguished individual finger movement activation within a 1cm cortical patch, revealing a topographical medial to lateral layout for the little finger to index to thumb. These findings demonstrate that the BOLD signal at 7 T is strongly correlated with the underlying electrophysiology, and is capable of discriminating patterns of neuronal population activity at a millimeter scale. The results further indicate the utility of 7 T fMRI for investigation of intra-area organization of function and network dynamics.

  4. Solving non-Markovian open quantum systems with multi-channel reservoir coupling

    SciTech Connect

    Broadbent, Curtis J.; Jing, Jun; Yu, Ting; Eberly, Joseph H.

    2012-08-15

    We extend the non-Markovian quantum state diffusion (QSD) equation to open quantum systems which exhibit multi-channel coupling to a harmonic oscillator reservoir. Open quantum systems which have multi-channel reservoir coupling are those in which canonical transformation of reservoir modes cannot reduce the number of reservoir operators appearing in the interaction Hamiltonian to one. We show that the non-Markovian QSD equation for multi-channel reservoir coupling can, in some cases, lead to an exact master equation which we derive. We then derive the exact master equation for the three-level system in a vee-type configuration which has multi-channel reservoir coupling and give the analytical solution. Finally, we examine the evolution of the three-level vee-type system with generalized Ornstein-Uhlenbeck reservoir correlations numerically. - Highlights: Black-Right-Pointing-Pointer The concept of multi-channel vs. single-channel reservoir coupling is rigorously defined. Black-Right-Pointing-Pointer The non-Markovian quantum state diffusion equation for arbitrary multi-channel reservoir coupling is derived. Black-Right-Pointing-Pointer An exact time-local master equation is derived under certain conditions. Black-Right-Pointing-Pointer The analytical solution to the three-level system in a vee-type configuration is found. Black-Right-Pointing-Pointer The evolution of the three-level system under generalized Ornstein-Uhlenbeck noise is plotted for many parameter regimes.

  5. Experimental and numerical analysis of B1(+) field and SAR with a new transmit array design for 7T breast MRI.

    PubMed

    Kim, Junghwan; Krishnamurthy, Narayan; Santini, Tales; Zhao, Yujuan; Zhao, Tiejun; Bae, Kyongtae Ty; Ibrahim, Tamer S

    2016-08-01

    Developing a radiofrequency (RF) coil system that produces a uniform B1(+) field (circularly polarized component of the transverse magnetic field responsible for excitation) and low specific absorption rate (SAR) is critical for high performance ultrahigh field human imaging. In this study, we provide the design of a new eight channel radiofrequency (RF) transmit (Tx) array for breast MRI at 7T. A numerical analysis utilizing an in-house finite difference time domain (FDTD) package was carried out in (1) four breast models, (2) homogeneous spherical model and (3) full body model to calculate the B1(+) intensity (μT) and homogeneity represented by coefficient of variation (CoV=standard deviation/mean) in the proposed RF array design. The numerical results were compared with that measured in breast phantom (Bphantom) and homogeneous spherical phantom at 7T MRI and showed very good agreement. Average and peak SARs were also calculated in the four breast models and the temperature rises due to the operation of the RF array were also measured in the Bphantom. The proposed RF array; which can operate in a single or multi transmit modes, demonstrates homogeneous RF field excitation with acceptable local/average SAR levels for breast MRI at 7T.

  6. Fusion in diffusion MRI for improved fibre orientation estimation: An application to the 3T and 7T data of the Human Connectome Project.

    PubMed

    Sotiropoulos, Stamatios N; Hernández-Fernández, Moisés; Vu, An T; Andersson, Jesper L; Moeller, Steen; Yacoub, Essa; Lenglet, Christophe; Ugurbil, Kamil; Behrens, Timothy E J; Jbabdi, Saad

    2016-07-01

    Determining the acquisition parameters in diffusion magnetic resonance imaging (dMRI) is governed by a series of trade-offs. Images of lower resolution have less spatial specificity but higher signal to noise ratio (SNR). At the same time higher angular contrast, important for resolving complex fibre patterns, also yields lower SNR. Considering these trade-offs, the Human Connectome Project (HCP) acquires high quality dMRI data for the same subjects at different field strengths (3T and 7T), which are publically released. Due to differences in the signal behavior and in the underlying scanner hardware, the HCP 3T and 7T data have complementary features in k- and q-space. The 3T dMRI has higher angular contrast and resolution, while the 7T dMRI has higher spatial resolution. Given the availability of these datasets, we explore the idea of fusing them together with the aim of combining their benefits. We extend a previously proposed data-fusion framework and apply it to integrate both datasets from the same subject into a single joint analysis. We use a generative model for performing parametric spherical deconvolution and estimate fibre orientations by simultaneously using data acquired under different protocols. We illustrate unique features from each dataset and how they are retained after fusion. We further show that this allows us to complement benefits and improve brain connectivity analysis compared to analyzing each of the datasets individually. PMID:27071694

  7. Experimental and numerical analysis of B1+ field and SAR with a new transmit array design for 7 T breast MRI

    NASA Astrophysics Data System (ADS)

    Kim, Junghwan; Krishnamurthy, Narayan; Santini, Tales; Zhao, Yujuan; Zhao, Tiejun; Bae, Kyongtae Ty; Ibrahim, Tamer S.

    2016-08-01

    Developing a radiofrequency (RF) coil system that produces a uniform B1+ field (circularly polarized component of the transverse magnetic field responsible for excitation) and low specific absorption rate (SAR) is critical for high performance ultrahigh field human imaging. In this study, we provide the design of a new eight channel radiofrequency (RF) transmit (Tx) array for breast MRI at 7 T. A numerical analysis utilizing an in-house finite difference time domain (FDTD) package was carried out in (1) four breast models, (2) homogeneous spherical model and (3) full body model to calculate the B1+ intensity (μT) and homogeneity represented by coefficient of variation (CoV = standard deviation/mean) in the proposed RF array design. The numerical results were compared with that measured in breast phantom (Bphantom) and homogeneous spherical phantom at 7 T MRI and showed very good agreement. Average and peak SARs were also calculated in the four breast models and the temperature rises due to the operation of the RF array were also measured in the Bphantom. The proposed RF array; which can operate in a single or multi transmit modes, demonstrates homogeneous RF field excitation with acceptable local/average SAR levels for breast MRI at 7 T.

  8. Adaptive Multichannel Radiation Sensors for Plant Parameter Monitoring

    NASA Astrophysics Data System (ADS)

    Mollenhauer, Hannes; Remmler, Paul; Schuhmann, Gudrun; Lausch, Angela; Merbach, Ines; Assing, Martin; Mollenhauer, Olaf; Dietrich, Peter; Bumberger, Jan

    2016-04-01

    Nutrients such as nitrogen are playing a key role in the plant life cycle. They are much needed for chlorophyll production and other plant cell components. Therefore, the crop yield is strongly affected by plant nutrient status. Due to the spatial and temporal variability of soil characteristics or swaying agricultural inputs the plant development varies within a field. Thus, the determination of these fluctuations in the plant development is valuable for a detection of stress conditions and optimization of fertilisation due to its high environmental and economic impact. Plant parameters play crucial roles in plant growth estimation and prediction since they are used as indicators of plant performance. Especially indices derived out of remote sensing techniques provide quantitative information about agricultural crops instantaneously, and above all, non-destructively. Due to the specific absorption of certain plant pigments, a characteristic spectral signature can be seen in the visible and IR part of the electromagnetic spectrum, known as narrow-band peaks. In an analogous manner, the presence and concentration of different nutrients cause a characteristic spectral signature. To this end, an adequate remote sensing monitoring concept is needed, considering heterogeneity and dynamic of the plant population and economical aspects. This work will present the development and field investigations of an inexpensive multichannel radiation sensor to observe the incoming and reflected specific parts or rather distinct wavelengths of the solar light spectrum on the crop and facilitate the determination of different plant indices. Based on the selected sensor wavelengths, the sensing device allows the detection of specific parameters, e.g. plant vitality, chlorophyll content or nitrogen content. Besides the improvement of the sensor characteristic, the simple wavelength adaption, and the price-performance ratio, the achievement of appropriate energy efficiency as well as a

  9. MO-H-19A-04: Multichannel CW Ultrasonic Thermometry for Imaging Therapeutic Dose Fields in Water

    SciTech Connect

    Tosh, R

    2014-06-15

    Purpose: To develop a scalable, multichannel ultrasonic thermometry system suitable for imaging clinical-beam dose distributions in a water phantom. Method: A small, glass-walled rectangular water phantom (15 cm × 20 cm × 30 cm) was filled with distilled water, and two ultrasonic transducers were placed on the outside, against opposing walls, approximately 5 cm below the water line, and were aligned to optimize transmission/reception of ultrasound between them. Two synchronized lock-in amplifiers were connected to the transducers to enable full-duplex operation of two separate ultrasonic frequency channels configured to transmit simultaneously through the same volume of water and thereby provide independent measurements of the temperature-dependent ultrasonic phase lag. Controlled heating of the water via immersed power resistors provided a means to study dependence of measured phase lag on temperature change for both channels; cross-correlation of the phase outputs enabled much smaller temperature fluctuations in the phantom to be used to ascertain the noise floor and achievable temperature resolution. Results: Temperature measurements from both channels, converted from phase measurements via polynomials available in the literature, exhibited the expected linear dependence of ultrasonic phase on temperature change (measured via calibrated thermistor probe). Cross-correlation analysis of phase fluctuations yielded rms noise estimates of approximately 1-2 microKelvin, comparable to that observed in standard water calorimeters. Conclusion: Phase-sensitive detection of cw ultrasound has been shown to provide temperature sensitivity needed for calorimetry of external treatment beams, and the present simple demonstration establishes that multiple channels may be run simultaneously without phase disturbances that currently affect time-of-flight techniques utilizing phase-detection. Immediate plans include doubling the number of sensors, to enable a simple tomographic

  10. Semiclassical multichannel perturbed-stationary-state model for rearrangement atomic collisions

    NASA Astrophysics Data System (ADS)

    Hose, Gabriel

    1995-03-01

    We present a translationally invariant formulation of the semiclassical perturbed-stationary-state (PSS) method of atomic collisions that satisfies scattering boundary conditions without resorting to the electron translation factor. Our formulation hinges on the fact that correctly dissociating linear combinations of adiabatic electronic states become in the limit proper atomic states. Galilean invariant dynamical couplings are generated by scattering momenta conjugated to reaction coordinates in the Jacobi frames appropriate for describing either the colliding or the parting atomic species. Residual asymptotic couplings exist and constitute a necessary ingredient of our theory. They emerge because an electron in asymptotic capture (charge-exchange) state travels in the Jacobi frame proper for its collision entry state. As such, we do not eliminate the residual couplings by modifying the adiabatic functions with an electron translation factor, but rather harness them to construct asymptotic interaction-picture traveling states suitable for the PSS basis employed. This allows negating the traveling phases from the semiclassically propagated adiabatic amplitudes. The resulting phase-free capture amplitudes reach a definite asymptotic limit. The collision momentum operators in Jacobi coordinates proper for different asymptotic rearrangements are not equivalent. This is always true regardless of the basis employed, since imposing a diagonal internal kinetic energy in one Jacobi frame necessarily implies it is not diagonal in other internal coordinates (which is also the source of residual couplings). We therefore suggest a unique and instantaneous dynamical coupling operator may be constructed as the temporal adiabatic-state weighted average of the scattering momenta associated with the electronic rearrangements spanned by the basis. The proposed multichannel PSS propagator is shown, in forthcoming work, to faithfully reproduce the charge-exchange cross sections in

  11. A 94/183 GHz multichannel radiometer for Convair flights

    NASA Technical Reports Server (NTRS)

    Gagliano, J. A.; Stratigos, J. A.; Forsythe, R. E.; Schuchardt, J. M.

    1979-01-01

    A multichannel 94/183 GHz radiometer was designed, built, and installed on the NASA Convair 990 research aircraft to take data for hurricane penetration flights, SEASAT-A underflights for measuring rain and water vapor, and Nimbus-G underflights for new sea ice signatures and sea surface temperature data (94 GHz only). The radiometer utilized IF frequencies of 1, 5, and 8.75 GHz about the peak of the atmospheric water vapor absorption line, centered at 183.3 GHz, to gather data needed to determine the shape of the water molecule line. Another portion of the radiometer operated at 94 GHz and obtained data on the sea brightness temperature, sea ice signatures, and on areas of rain near the ocean surface. The radiometer used a multiple lens antenna/temperature calibration technique using 3 lenses and corrugated feed horns at 94 GHz and 183 GHz. Alignment of the feed beams at 94 GHz and 183 GHz was accomplished using a 45 deg oriented reflecting surface which permitted simultaneous viewing of the feeds on alternate cycles of the chopping intervals.

  12. A research of a high precision multichannel data acquisition system

    NASA Astrophysics Data System (ADS)

    Zhong, Ling-na; Tang, Xiao-ping; Yan, Wei

    2013-08-01

    The output signals of the focusing system in lithography are analog. To convert the analog signals into digital ones which are more flexible and stable to process, a desirable data acquisition system is required. The resolution of data acquisition, to some extent, affects the accuracy of focusing. In this article, we first compared performance between the various kinds of analog-to-digital converters (ADC) available on the market at the moment. Combined with the specific requirements (sampling frequency, converting accuracy, numbers of channels etc) and the characteristics (polarization, amplitude range etc) of the analog signals, the model of the ADC to be used as the core chip in our hardware design was determined. On this basis, we chose other chips needed in the hardware circuit that would well match with ADC, then the overall hardware design was obtained. Validation of our data acquisition system was verified through experiments and it can be demonstrated that the system can effectively realize the high resolution conversion of the multi-channel analog signals and give the accurate focusing information in lithography.

  13. Open-loop dereverberation of multichannel room impulse responses

    NASA Astrophysics Data System (ADS)

    Lee, Bowon; Hasegawa-Johnson, Mark A.; Goudeseune, Camille

    2003-04-01

    We are developing the audio display for a CAVE-type virtual reality theater, a 3-m cube with displays covering all six rigid faces. The user's headgear continuously reports ear positions so headphones would be possible, but we nevertheless prefer loudspeakers because this enhances the sense of total immersion. Because sounds produced at the loudspeakers are distorted by the room impulse responses, we therefore face the problem of controlling the sound at the listener's two ears. Our proposed solution consists of open-loop acoustic point control, i.e., dereverberation. The room impulse responses from each loudspeaker to each ear of the listener are inverted using multichannel inversion methods, to create exactly the desired sound field at the listener's ears. Because the actual room impulse responses cannot be measured in real time (as the listener walks around), instead the impulse responses simulated by the image-source method is used. A new evaluation criterion is proposed to quantitatively evaluate both the simulation and the open-loop dereverberation. The actual impulse responses used for this evaluation are measured with a starter pistol, since this best approximates the point source assumed by the image-source method.

  14. Multi-channel amplitude analyzer for x-ray investigations

    NASA Astrophysics Data System (ADS)

    Karetnikov, M. D.; Klimov, A. I.; Zaitsev, V. I.

    2005-07-01

    The suggested device is implemented as one-module instrument including: a spectrometric amplifier providing superposition rejection, basic level restoration, track-and-hold functions, a precision ADC completed with the buffer memory; high-voltage power supply for X-ray detector; hardware interface with PC. All this resulted in a compact, functionally completed instrument for X-ray analysis. The device is a convenient instrument for X-ray fluorescent analysis, radiation diffraction studies, determination of element composition of a substance, customs and forensic expertise, medical diagnostics, testing of food products for presence of heavy elements, and other studies associated with X-ray applications. The functional diagram of the multi-channel amplitude analyzer is given in Fig. 1. The control circuit includes programmable logic device (PLD) EPM7128AETC100-lO manufactured by Altera Corporation, high performance C8051A021 processor by Cygnal Integrated Products and AS7C3256-12TC static memory by Cypress.

  15. The SRI24 multichannel brain atlas: construction and applications

    NASA Astrophysics Data System (ADS)

    Rohlfing, Torsten; Zahr, Natalie M.; Sullivan, Edith V.; Pfefferbaum, Adolf

    2008-03-01

    We present a new standard atlas of the human brain based on magnetic resonance images. The atlas was generated using unbiased population registration from high-resolution images obtained by multichannel-coil acquisition at 3T in a group of 24 normal subjects. The final atlas comprises three anatomical channels (T I-weighted, early and late spin echo), three diffusion-related channels (fractional anisotropy, mean diffusivity, diffusion-weighted image), and three tissue probability maps (CSF, gray matter, white matter). The atlas is dynamic in that it is implicitly represented by nonrigid transformations between the 24 subject images, as well as distortion-correction alignments between the image channels in each subject. The atlas can, therefore, be generated at essentially arbitrary image resolutions and orientations (e.g., AC/PC aligned), without compounding interpolation artifacts. We demonstrate in this paper two different applications of the atlas: (a) region definition by label propagation in a fiber tracking study is enabled by the increased sharpness of our atlas compared with other available atlases, and (b) spatial normalization is enabled by its average shape property. In summary, our atlas has unique features and will be made available to the scientific community as a resource and reference system for future imaging-based studies of the human brain.

  16. Joint decorrelation, a versatile tool for multichannel data analysis.

    PubMed

    de Cheveigné, Alain; Parra, Lucas C

    2014-09-01

    We review a simple yet versatile approach for the analysis of multichannel data, focusing in particular on brain signals measured with EEG, MEG, ECoG, LFP or optical imaging. Sensors are combined linearly with weights that are chosen to provide optimal signal-to-noise ratio. Signal and noise can be variably defined to match the specific need, e.g. reproducibility over trials, frequency content, or differences between stimulus conditions. We demonstrate how the method can be used to remove power line or cardiac interference, enhance stimulus-evoked or stimulus-induced activity, isolate narrow-band cortical activity, and so on. The approach involves decorrelating both the original and filtered data by joint diagonalization of their covariance matrices. We trace its origins; offer an easy-to-understand explanation; review a range of applications; and chart failure scenarios that might lead to misleading results, in particular due to overfitting. In addition to its flexibility and effectiveness, a major appeal of the method is that it is easy to understand. PMID:24990357

  17. Quasiclassical theory of disordered multi-channel Majorana quantum wires

    NASA Astrophysics Data System (ADS)

    Neven, Patrick; Bagrets, Dmitry; Altland, Alexander

    2013-05-01

    Multi-channel spin-orbit quantum wires, when subjected to a magnetic field and proximity coupled to an s-wave superconductor, may support Majorana states. We study what happens to these systems in the presence of disorder. Inspired by the widely established theoretical methods of mesoscopic superconductivity, we develop á la Eilenberger a quasiclassical approach to topological nanowires valid in the limit of strong spin-orbit coupling. We find that the ‘Majorana number’ {\\cal M} , distinguishing between the state with Majorana fermions (symmetry class B) and no Majorana fermions (class D), is given by the product of two Pfaffians of gapped quasiclassical Green's functions fixed by the right and left terminals connected to the wire. A numerical solution of the Eilenberger equations reveals that the class D disordered quantum wires are prone to the formation of the zero-energy anomaly (class D impurity spectral peak) in the local density of states that shares the key features of the Majorana peak. In this way, we confirm the robustness of our previous conclusions (Bagrets and Altland 2012 Phys. Rev. Lett. 109 227005) on a more restrictive system setup. Generally speaking, we find that the quasiclassical approach provides a highly efficient means to address disordered class D superconductors both in the presence and in the absence of topological structures.

  18. Design of multichannel image processing on the Space Solar Telescope

    NASA Astrophysics Data System (ADS)

    Zhang, Bin

    2000-07-01

    The multi-channel image processing system on the Space Solar Telescope (SST) is described in this paper. This system is main part of science data unit (SDU), which is designed for dealing with the science data from every payload on the SST. First every payload on the SST and its scientific objective are introduced. They are main optic telescope, four soft X- ray telescopes, an H-alpha and white light (full disc) telescope, a coronagraph, a wide band X-ray and Gamma-ray spectrometer, and a solar and interplanetary radio spectrometer. Then the structure of SDU is presented. In this part, we discuss the hardware and software structure of SDU, which is designed for multi-payload. The science data scream of every payload is summarized, too. Solar magnetic and velocity field processing that occupies more than 90% of the data processing of SDU is discussed, which includes polarizing unit, image receiver and image adding unit. Last the plan of image data compression and mass memory that is designed for science data storage are presented.

  19. A low-noise receiver for multichannel wireless neural recording.

    PubMed

    Yin, Ming; Ghovanloo, M

    2008-01-01

    We present a high performance wideband receiver for multichannel wireless implantable neural recording systems (WINeR) utilizing pulse width modulation of time division multiplexed (PWM-TDM) samples. The receiver consists of a 50 MHz approximately 1 GHz tunable down-converter with 75 MHz bandwidth, frequency shift keying and PWM demodulators, and a high throughput USB interface. Several IF gain stages, passive LC filters, and an FPGA-based time-to-digital converter (TDC) with time interval resolution of 428 ps have significantly enhanced the receiver performance and extended its receiving range. A 2 MB SDRAM is used as a buffer between the TDC and USB to ensure continuous throughput for the digitized raw data at data rates up to 10 Mb/s. The receiver performance is evaluated with a 6-channel WINeR transmitter, showing that the entire system input referred noise with this receiver is 9.8 and 12.7 microV(rms) at 0.5 and 3.5 m distances, respectively, which are equivalent to 8.2 and 7.9 bits of resolution at 640 ksample/s.

  20. Threshold magnitudes for a multichannel correlation detector in background seismicity

    DOE PAGES

    Carmichael, Joshua D.; Hartse, Hans

    2016-04-01

    Colocated explosive sources often produce correlated seismic waveforms. Multichannel correlation detectors identify these signals by scanning template waveforms recorded from known reference events against "target" data to find similar waveforms. This screening problem is challenged at thresholds required to monitor smaller explosions, often because non-target signals falsely trigger such detectors. Therefore, it is generally unclear what thresholds will reliably identify a target explosion while screening non-target background seismicity. Here, we estimate threshold magnitudes for hypothetical explosions located at the North Korean nuclear test site over six months of 2010, by processing International Monitoring System (IMS) array data with a multichannelmore » waveform correlation detector. Our method (1) accounts for low amplitude background seismicity that falsely triggers correlation detectors but is unidentifiable with conventional power beams, (2) adapts to diurnally variable noise levels and (3) uses source-receiver reciprocity concepts to estimate thresholds for explosions spatially separated from the template source. Furthermore, we find that underground explosions with body wave magnitudes mb = 1.66 are detectable at the IMS array USRK with probability 0.99, when using template waveforms consisting only of P -waves, without false alarms. We conservatively find that these thresholds also increase by up to a magnitude unit for sources located 4 km or more from the Feb.12, 2013 announced nuclear test.« less

  1. Multi-Channel Transfer Function with Dimensionality Reduction

    PubMed Central

    Kim, Han Suk; Schulze, Jürgen P.; Cone, Angela C.; Sosinsky, Gina E.; Martone, Maryann E.

    2010-01-01

    The design of transfer functions for volume rendering is a difficult task. This is particularly true for multi-channel data sets, where multiple data values exist for each voxel. In this paper, we propose a new method for transfer function design. Our new method provides a framework to combine multiple approaches and pushes the boundary of gradient-based transfer functions to multiple channels, while still keeping the dimensionality of transfer functions to a manageable level, i.e., a maximum of three dimensions, which can be displayed visually in a straightforward way. Our approach utilizes channel intensity, gradient, curvature and texture properties of each voxel. The high-dimensional data of the domain is reduced by applying recently developed nonlinear dimensionality reduction algorithms. In this paper, we used Isomap as well as a traditional algorithm, Principle Component Analysis (PCA). Our results show that these dimensionality reduction algorithms significantly improve the transfer function design process without compromising visualization accuracy. In this publication we report on the impact of the dimensionality reduction algorithms on transfer function design for confocal microscopy data. PMID:20582228

  2. Single particle multichannel bio-aerosol fluorescence sensor

    NASA Astrophysics Data System (ADS)

    Kaye, P. H.; Stanley, W. R.; Hirst, E.; Foot, E. V.; Baxter, K. L.; Barrington, S. J.

    2005-05-01

    We describe a prototype low-cost multi-channel aerosol fluorescence sensor designed for unattended deployment in medium to large area bio-aerosol detection networks. Individual airborne particles down to ~1μm in size are detected and sized by measurement of light scattered from a continuous-wave diode laser (660nm). This scatter signal is then used to trigger the sequential firing of two xenon sources which irradiate the particle with UV pulses at ~280 nm and ~370 nm, optimal for excitation of bio-fluorophores tryptophan and NADH (nicotinamide adenine dinucleotide) respectively. For each excitation wavelength, fluorescence is detected across two bands embracing the peak emissions of the same bio-fluorophores. Current measurement rates are up to ~125 particles/s, corresponding to all particles for concentrations up to 1.3 x 104 particles/l. Developments to increase this to ~500 particles/s are in hand. Device sensitivity is illustrated in preliminary data recorded from aerosols of E.coli, BG spores, and a variety of non-biological materials.

  3. Wireless multichannel biopotential recording using an integrated FM telemetry circuit.

    PubMed

    Mohseni, Pedram; Najafi, Khalil; Eliades, Steven J; Wang, Xiaoqin

    2005-09-01

    This paper presents a four-channel telemetric microsystem featuring on-chip alternating current amplification, direct current baseline stabilization, clock generation, time-division multiplexing, and wireless frequency-modulation transmission of microvolt- and millivolt-range input biopotentials in the very high frequency band of 94-98 MHz over a distance of approximately 0.5 m. It consists of a 4.84-mm2 integrated circuit, fabricated using a 1.5-microm double-poly double-metal n-well standard complementary metal-oxide semiconductor process, interfaced with only three off-chip components on a custom-designed printed-circuit board that measures 1.7 x 1.2 x 0.16 cm3, and weighs 1.1 g including two miniature 1.5-V batteries. We characterize the microsystem performance, operating in a truly wireless fashion in single-channel and multichannel operation modes, via extensive benchtop and in vitro tests in saline utilizing two different micromachined neural recording microelectrodes, while dissipating approximately 2.2 mW from a 3-V power supply. Moreover, we demonstrate successful wireless in vivo recording of spontaneous neural activity at 96.2 MHz from the auditory cortex of an awake marmoset monkey at several transmission distances ranging from 10 to 50 cm with signal-to-noise ratios in the range of 8.4-9.5 dB.

  4. Observations of Coronal Mass Ejections with the Coronal Multichannel Polarimeter

    NASA Astrophysics Data System (ADS)

    Tian, H.; Tomczyk, S.; McIntosh, S. W.; Bethge, C.; de Toma, G.; Gibson, S.

    2013-12-01

    The Coronal Multichannel Polarimeter (CoMP) measures not only the polarization of coronal emission, but also the full radiance profiles of coronal emission lines. For the first time, CoMP observations provide high-cadence image sequences of the coronal line intensity, Doppler shift, and line width simultaneously over a large field of view. By studying the Doppler shift and line width we may explore more of the physical processes of the initiation and propagation of coronal mass ejections (CMEs). Here we identify a list of CMEs observed by CoMP and present the first results of these observations. Our preliminary analysis shows that CMEs are usually associated with greatly increased Doppler shift and enhanced line width. These new observations provide not only valuable information to constrain CME models and probe various processes during the initial propagation of CMEs in the low corona, but also offer a possible cost-effective and low-risk means of space-weather monitoring.

  5. Speech perception and functional benefit after multichannel cochlear implantation.

    PubMed

    Välimaa, T T; Sorri, M J; Löppönen, H J

    2001-01-01

    This study was done to investigate the effect of a multichannel cochlear implant on speech perception and the functional benefit of cochlear implantation in Finnish-speaking postlingually deafened adults. Fourteen subjects were enrolled. Sentence and word recognition were studied with open-set tests auditorily only. One year after implantation, the listening performance was assessed by case histories and interviews. Before implantation for subjects with a hearing aid, the mean recognition score was 38% for sentences and 17% for words. One year after switching on the implant, the mean recognition score was 84% for sentences and 70% for words. Before implantation, the majority of the subjects were not aware of environmental sounds and only a few were able to recognize some environmental sounds. One year after switching on the implant, the majority of the subjects were able to use the telephone with a familiar speaker. All the subjects were able to recognize speech auditorily only and had thus gained good functional benefit from the implant.

  6. A robotic multi-channel platform for interstitial photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Sharikova, Anna V.; Finlay, Jarod C.; Dimofte, Andreea; Zhu, Timothy C.

    2013-03-01

    A custom-made robotic multichannel platform for interstitial photodynamic therapy (PDT) and diffuse optical tomography (DOT) was developed and tested in a phantom experiment. The system, which was compatible with the operating room (OR) environment, had 16 channels for independent positioning of light sources and/or isotropic detectors in separate catheters. Each channel's motor had an optical encoder for position feedback, with resolution of 0.05 mm, and a maximum speed of 5 cm/s. Automatic calibration of detector positions was implemented using an optical diode beam that defined the starting position of each motor, and by means of feedback algorithms controlling individual channels. As a result, the accuracy of zero position of 0.1 mm for all channels was achieved. We have also employed scanning procedures where detectors automatically covered the appropriate range around source positions. Thus, total scan time for a typical optical properties (OP) measurement throughout the phantom was about 1.5 minutes with point sources. The OP were determined based on the measured light fluence rates. These enhancements allow a tremendous improvement of treatment quality for a bulk tumor compared to the systems employed in previous clinical trials.

  7. Multichannel waveguides for the simultaneous detection of disease biomarkers

    SciTech Connect

    Mukundan, Harshini; Price, Dominique Z; Grace, Wynne K; Swanson, Basil I

    2009-01-01

    The sensor team at the Los Alamos National Laboratory has developed a waveguide-based optical biosensor that has previously been used for the detection of biomarkers associated with diseases such as tuberculosis, breast cancer, anthrax and influenza in complex biological samples (e.g., serum and urine). However, no single biomarker can accurately predict disease. To address this issue, we developed a multiplex assay for the detection of components of the Bacillus anthracis lethal toxin on single mode planar optical waveguides with tunable quantum dots as the fluorescence reporter. This limited ability to multiplex is still insufficient for accurate detection of disease or for monitoring prognosis. In this manuscript, we demonstrate for the first time, the design, fabrication and successful evaluation of a multichannel planar optical waveguide for the simultaneous detection of at least three unknown samples in quadruplicate. We demonstrate the simultaneous, rapid (30 min), quantitative (with internal standard) and sensitive (limit of detection of 1 pM) detection of protective antigen and lethal factor of Bacillus anthracis in complex biological samples (serum) using specific monoclonal antibodies labeled with quantum dots as the fluorescence reporter.

  8. High transformer ratio of multi-channel dielectric wakefield structures

    NASA Astrophysics Data System (ADS)

    Shchelkunov, Sergey V.; Marshall, Thomas C.; Sotnikov, Gennadij V.; Hirshfield, Jay L.

    2016-09-01

    Dielectric wakefield (DWA) accelerator concepts are receiving attention on account of their promising performance, mechanical simplicity, and anticipated low cost. Interest in DWA physics directed toward an advanced high-gradient accelerator has been enhanced by a finding that some dielectrics can withstand very high fields (>1 GV/m) for the short times during the passage of charged bunches along dielectric-lined channels. In a two-channel structure, a drive bunch train propagates in a first channel, and in the second adjacent channel where a high gradient wakefield develops, a witness bunch is accelerated. Compared with single-channel DWA's, a two-beam accelerator delivers a high transformer ratio, and thereby reduces the number of drive beam sections needed to achieve a given final test beam energy. An overview of multi-channel DWA structures will be given, with an emphasis on two-channel structures, presenting their advantages and drawbacks, and potential impact on the field. Studies aimed to examine charging rate and charge distribution in a thin walled dielectric wakefield accelerator from a passing charge bunch and the physics of conductivity and discharge phenomena in dielectric materials useful for such accelerator applications are presented in a separate paper in the EAAC-2015 conference proceedings.

  9. A scalable, fast, and multichannel arbitrary waveform generator

    NASA Astrophysics Data System (ADS)

    Baig, M. T.; Johanning, M.; Wiese, A.; Heidbrink, S.; Ziolkowski, M.; Wunderlich, C.

    2013-12-01

    This article reports on the development of a multichannel arbitrary waveform generator that simultaneously generates arbitrary voltage waveforms on 24 independent channels with a dynamic update rate of up to 25 Msps. A real-time execution of a single waveform and/or sequence of multiple waveforms in succession, with a user programmable arbitrary sequence order is provided under the control of a stand-alone sequencer circuit implemented using a field programmable gate array. The device is operated using an internal clock and can be synced to other devices by means of transistor-transistor logic (TTL) pulses. The device can provide up to 24 independent voltages in the range of up to ± 9 V with a dynamic update-rate of up to 25 Msps and a power consumption of less than 35 W. Every channel can be programmed for 16 independent arbitrary waveforms that can be accessed during run time with a minimum switching delay of 160 ns. The device has a low-noise of 250 μVrms and provides a stable long-term operation with a drift rate below 10 μV/min and a maximum deviation less than ± 300 μVpp over a period of 2 h.

  10. A scalable, fast, and multichannel arbitrary waveform generator.

    PubMed

    Baig, M T; Johanning, M; Wiese, A; Heidbrink, S; Ziolkowski, M; Wunderlich, C

    2013-12-01

    This article reports on the development of a multichannel arbitrary waveform generator that simultaneously generates arbitrary voltage waveforms on 24 independent channels with a dynamic update rate of up to 25 Msps. A real-time execution of a single waveform and/or sequence of multiple waveforms in succession, with a user programmable arbitrary sequence order is provided under the control of a stand-alone sequencer circuit implemented using a field programmable gate array. The device is operated using an internal clock and can be synced to other devices by means of transistor-transistor logic (TTL) pulses. The device can provide up to 24 independent voltages in the range of up to ± 9 V with a dynamic update-rate of up to 25 Msps and a power consumption of less than 35 W. Every channel can be programmed for 16 independent arbitrary waveforms that can be accessed during run time with a minimum switching delay of 160 ns. The device has a low-noise of 250 μV(rms) and provides a stable long-term operation with a drift rate below 10 μV/min and a maximum deviation less than ± 300 μV(pp) over a period of 2 h.

  11. A multi-channel distributed DAQ for n-TPC

    NASA Astrophysics Data System (ADS)

    Cheng, Xiao-Lei; Liu, Jian-Fang; Yu, Qian; Niu, Li-Bo; Li, Yu-Lan

    2015-11-01

    A new fast neutron spectrometer named n-TPC has been designed by LPRI (Key Laboratory of Particle & Radiation Imaging, Ministry of Education) at Tsinghua University. The neutron energy spectrum can be calculated from the recoil angle and energy of the recoil proton detected by a 704-pad GEM-TPC. In beam tests at IHIP (Institute of Heavy Ion Physics, Peking University) in 2014, n-TPC performed better than 6%@6 MeV energy resolution and 5‰ detection efficiency. To find the best working parameters (the component and proportion of the gas, the high voltage between each GEM layer, etc.) of the n-TPC and support its application in various conditions, a multichannel distributed DAQ has been designed to read out the signals from the 704 channels. With over 25 Ms/s sampling rate and 12 bit resolution for each channel, it can record the time and amplitude information as well as traditional DAQs in the TPC application domain. The main design objective of this distributed DAQ, however, is more flexible parameter modulation and operation. It can support the n-TPC without the limitation of the chassis and categorize signals arriving from the 704 channels at the same time by different events without event triggers. Supported by National Natural Science Foundation of China (11275109)

  12. Biomimetic Micropatterned Multi-channel Nerve Guides by Templated Electrospinning

    PubMed Central

    Jeffries, Eric; Wang, Yadong

    2012-01-01

    This report describes a new approach for fabricating micro-channels within three-dimensional electrospun constructs. These key features serve to mimic the fascicular architecture and fibrous extracellular matrix found in native nerve. Both electrospun fibers and multi-channeled structure nerve guides have become areas of increasing interest for their beneficial roles in nerve repair. However, to the best of our knowledge, this is the first report of a guide that incorporates both. Multiple parallel channels provide a greater number of defined paths and increased surface area compared to cylindrical guides. Additionally, the fibrous nature of electrospun fibers permits better mass transport than solid-walled constructs. The flexible fabrication scheme allows tailoring of nerve guide parameters such as channel diameters ranging from 33-176μm and various wall thicknesses. Channel and fiber structures were assessed by optical and electron microscope images. Geometric calculations estimated a porosity of over 85% for these guides with 16% or less from the channels. In vitro culture with Schwann cells demonstrated cellular infiltration into channels with restricted migration between fibers. Finally, cell proliferation and survival throughout the guide indicates that this design warrants future in vivo examination. PMID:22179932

  13. 12C+12C fusion in a multichannel folding model

    NASA Astrophysics Data System (ADS)

    Assunção, M.; Descouvemont, P.

    2016-01-01

    The 12C+12C fusion reaction is investigated using a folding potential in a multichannel approach involving the 12C(0+1, 2+, 0+2, 3-) states. The 12C densities (including transition densities) are taken from the RGM calculation of Kamimura. For the nucleon-nucleon interaction, we use the DDM3Y density-dependent interaction. Owing to the explicit presence of inelastic channels, the imaginary part of the optical potential only contains a short-range fusion contribution. The S-factor is then virtually insensitive to the precise value, and the model is free of any fitting parameter. From the coupled-channel system, we determine the elastic and fusion cross sections simultaneously. As elastic data are available around the Coulomb barrier, this simultaneous treatment offers a good test for the reliability of the model. In the fusion cross section, the role of the inelastic channels and, in particular of the 12C(0+1)+12C(0+2) channel involving the Hoyle state, is discussed.

  14. Gauge transformations in multichannel laser-interaction Hamiltonians

    NASA Astrophysics Data System (ADS)

    Armstrong, G. S. J.; Esry, B. D.

    2015-05-01

    In our previous studies of molecular photodissociation, we solved the time-dependent Schrödinger equation in full dimensionality, casting the laser-molecule interaction in a length-gauge form. The nuclear wave function is then expanded on a basis of symmetric top functions in the angular coordinates. However, a velocity gauge representation of the nuclear motion may be advantageous, and may reduce the number of partial waves required in the angular basis expansion. In molecular problems, the standard transformation between length and velocity gauge must take account of the presence of short-range non-linear radial dependence of the dipole. In problems involving a single channel, the short-range behavior is not removed by the gauge transformation, leading to a short-range mixed-gauge Hamiltonian. Having derived the form of this Hamiltonian, we extend our analysis to multichannel problems, where the gauge transformation is further complicated by off-diagonal dipole terms. We examine the impact of this transformation in full-dimensional calculations, particularly its effectiveness in reducing the required size of the angular basis. This work is supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S.A.

  15. Multichannel analysis of surface wave method with the autojuggie

    USGS Publications Warehouse

    Tian, G.; Steeples, D.W.; Xia, J.; Miller, R.D.; Spikes, K.T.; Ralston, M.D.

    2003-01-01

    The shear (S)-wave velocity of near-surface materials and its effect on seismic-wave propagation are of fundamental interest in many engineering, environmental, and groundwater studies. The multichannel analysis of surface wave (MASW) method provides a robust, efficient, and accurate tool to observe near-surface S-wave velocity. A recently developed device used to place large numbers of closely spaced geophones simultaneously and automatically (the 'autojuggie') is shown here to be applicable to the collection of MASW data. In order to demonstrate the use of the autojuggie in the MASW method, we compared high-frequency surface-wave data acquired from conventionally planted geophones (control line) to data collected in parallel with the automatically planted geophones attached to steel bars (test line). The results demonstrate that the autojuggie can be applied in the MASW method. Implementation of the autojuggie in very shallow MASW surveys could drastically reduce the time required and costs incurred in such surveys. ?? 2003 Elsevier Science Ltd. All rights reserved.

  16. The Optimum Loudspeaker Arrangements for Multichannel Sound System

    NASA Astrophysics Data System (ADS)

    Hiyama, Koichiro; Komiyama, Setsu; Hamasaki, Kimio

    2002-09-01

    This paper discusses the number of loudspeakers for multichannel sound systems to reproduce the spatial impression of diffuse sound field, such as in auditorium. Some subjective experiments were conducted in order to find suitable numbers and arrangement of loudspeakers. On the experiments, reference diffuse sound filed was produced by 24 loudspeakers that were placed at every 15 degrees along a concentric circle around the listener in an anechoic room. And then, the number of loudspeakers, which radiated sound sources or reverberations, was reduced from 24 to 12, 8, 6, 4, 3, 2 and then each spatial impression was compared with the reference sound of 24 loudspeakers. For the sound source of these experiments, noises and musical sounds were used. It becomes clear that the spatial impression of diffuse sound field can be reproduced by only two symmetrical pairs of loudspeakers (that is, four loudspeakers in all). On this arrangement, one pair of loudspeakers should be place in the frontal area around the listener with in angle of about 60 deg, and the other pair should be in the rear area with an angle of 120 to 180 deg.

  17. Spatial mapping of dynamic cerebral autoregulation by multichannel near-infrared spectroscopy in high-grade carotid artery disease

    NASA Astrophysics Data System (ADS)

    Reinhard, Matthias; Schumacher, F. Konrad; Rutsch, Sebastian; Oeinck, Maximilian; Timmer, Jens; Mader, Irina; Schelter, Björn; Weiller, Cornelius; Kaller, Christoph P.

    2014-09-01

    The exact spatial distribution of impaired cerebral autoregulation in carotid artery disease is unknown. In this pilot study, we present a new approach of multichannel near-infrared spectroscopy (mcNIRS) for noninvasive spatial mapping of dynamic autoregulation in carotid artery disease. In 15 patients with unilateral severe carotid artery stenosis or occlusion, cortical hemodynamics in the bilateral frontal cortex were assessed from changes in oxyhemoglobin concentration using 52-channel NIRS (spatial resolution ˜2 cm). Dynamic autoregulation was graded by the phase shift between respiratory-induced 0.1 Hz oscillations of blood pressure and oxyhemoglobin. Ten of 15 patients showed regular phase values in the expected (patho) physiological range. Five patients had clearly outlying irregular phase values mostly due to artifacts. In patients with a regular phase pattern, a significant side-to-side difference of dynamic autoregulation was observed for the cortical border zone area between the middle and anterior cerebral artery (p<0.05). In conclusion, dynamic cerebral autoregulation can be spatially assessed from slow hemodynamic oscillations with mcNIRS. In high-grade carotid artery disease, cortical dynamic autoregulation is affected mostly in the vascular border zone. Spatial mapping of dynamic autoregulation may serve as a powerful tool for identifying brain regions at specific risks for hemodynamic infarction.

  18. Improvements of Travel-time Tomography Models from Joint Inversion of Multi-channel and Wide-angle Seismic Data

    NASA Astrophysics Data System (ADS)

    Begović, Slaven; Ranero, César; Sallarès, Valentí; Meléndez, Adrià; Grevemeyer, Ingo

    2016-04-01

    Commonly multichannel seismic reflection (MCS) and wide-angle seismic (WAS) data are modeled and interpreted with different approaches. Conventional travel-time tomography models using solely WAS data lack the resolution to define the model properties and, particularly, the geometry of geologic boundaries (reflectors) with the required accuracy, specially in the shallow complex upper geological layers. We plan to mitigate this issue by combining these two different data sets, specifically taking advantage of the high redundancy of multichannel seismic (MCS) data, integrated with wide-angle seismic (WAS) data into a common inversion scheme to obtain higher-resolution velocity models (Vp), decrease Vp uncertainty and improve the geometry of reflectors. To do so, we have adapted the tomo2d and tomo3d joint refraction and reflection travel time tomography codes (Korenaga et al, 2000; Meléndez et al, 2015) to deal with streamer data and MCS acquisition geometries. The scheme results in a joint travel-time tomographic inversion based on integrated travel-time information from refracted and reflected phases from WAS data and reflected identified in the MCS common depth point (CDP) or shot gathers. To illustrate the advantages of a common inversion approach we have compared the modeling results for synthetic data sets using two different travel-time inversion strategies: We have produced seismic velocity models and reflector geometries following typical refraction and reflection travel-time tomographic strategy modeling just WAS data with a typical acquisition geometry (one OBS each 10 km). Second, we performed joint inversion of two types of seismic data sets, integrating two coincident data sets consisting of MCS data collected with a 8 km-long streamer and the WAS data into a common inversion scheme. Our synthetic results of the joint inversion indicate a 5-10 times smaller ray travel-time misfit in the deeper parts of the model, compared to models obtained using just

  19. Advanced technology for a satellite multichannel demultiplexer/demodulator

    NASA Technical Reports Server (NTRS)

    Abramovitz, Irwin J.; Flechsig, Drew E.; Matteis, Richard M., Jr.

    1994-01-01

    Satellite on-board processing is needed to efficiently service multiple users while at the same time minimizing earth station complexity. The processing satellite receives a wideband uplink at 30 GHz and down-converts it to a suitable intermediate frequency. A multichannel demultiplexer then separates the composite signal into discrete channels. Each channel is then demodulated by bulk demodulators, with the baseband signals routed to the downlink processor for retransmission to the receiving earth stations. This type of processing circumvents many of the difficulties associated with traditional bent-pipe repeater satellites. Uplink signal distortion and interference are not retransmitted on the downlink. Downlink power can be allocated in accordance with user needs, independent of uplink transmissions. This allows the uplink users to employ different data rates as well as different modulation and coding schemes. In addition, all downlink users have a common frequency standard and symbol clock on the satellite, which is useful for network synchronization in time division multiple access schemes. The purpose of this program is to demonstrate the concept of an optically implemented multichannel demultiplexer (MCD). A proof-of-concept (POC) model has been developed which has the ability to receive a 40 MHz wide composite signal consisting of up to 1000 40 kHz QPSK modulated channels and perform the demultiplexing process. In addition a set of special test equipment (STE) has been configured to evaluate the performance of the POC model. The optical MCD is realized as an acousto-optic spectrum analyzer utilizing the capability of Bragg cells to perform the required channelization. These Bragg cells receive an optical input from a laser source and an RF input (the signal). The Bragg interaction causes optical output diffractions at angles proportional to the RF input frequency. These discrete diffractions are optically detected and output to individual demodulators for

  20. Detection of moving objects using multi-channel kernel fuzzy correlogram based background subtraction.

    PubMed

    Chiranjeevi, Pojala; Sengupta, Somnath

    2014-06-01

    In this paper, we examine the suitability of correlogram for background subtraction, as a step towards moving object detection. Correlogram captures inter-pixel relationships in a region and is seen to be effective for modeling the dynamic backgrounds. A multi-channel correlogram is proposed using inter-channel and intra-channel correlograms to exploit full color information and the inter-pixel relations on the same color planes and across the planes. We thereafter derive a novel feature, termed multi-channel kernel fuzzy correlogram, composed by applying a fuzzy membership transformation over multi-channel correlogram. Multi-channel kernel fuzzy correlogram maps multi-channel correlogram into a reduced dimensionality space and is less sensitivity to noise. The approach handles multimodal distributions without using multiple models per pixel unlike traditional approaches. The approach does not require ideal background frames for background model initialization and can be initialized with moving objects also. Effectiveness of the proposed method is illustrated on different video sequences. PMID:24108723

  1. Reproducibility and optimization of in vivo human diffusion-weighted MRS of the corpus callosum at 3T and 7T

    PubMed Central

    Branzoli, Francesca; Webb, Andrew; Sati, Pascal; Reich, Daniel S.; Ronen, Itamar

    2016-01-01

    Diffusion-weighted MRS (DWS) of brain metabolites enables the study of cell-specific alterations in tissue microstructure by probing the diffusion of intracellular metabolites. In particular, the diffusion properties of neuronal N-acetylaspartate (NAA), typically co-measured with N-acetylaspartyl glutamate (NAAG) (NAA + NAAG = tNAA), have been shown to be sensitive to intraneuronal/axonal damage in pathologies such as stroke and multiple sclerosis. Lacking, so far, are empirical assessments of the reproducibility of DWS measures across time and subjects, as well as a systematic investigation of the optimal acquisition parameters for DWS experiments, both of which are sorely needed for clinical applications of the method. In this study, we acquired comprehensive single-volume DWS datasets of the human corpus callosum at 3T and 7T. We investigated the inter- and intra-subject variability of empirical and modeled diffusion properties of tNAA [Davg(tNAA) and Dmodel(tNAA), respectively]. Subsequently, we used a jackknife-like resampling approach to explore the variance of these properties in partial data subsets reflecting different total scan durations. The coefficients of variation (CV) and repeatability coefficients (CR) for Davg(tNAA) and Dmodel(tNAA) were calculated for both 3T and 7T, with overall lower variability in the 7T results. Although this work is limited to the estimation of the diffusion properties in the corpus callosum, we show that a careful choice of diffusion-weighting conditions at both field strengths allows the accurate measurement of tNAA diffusion properties in clinically relevant experimental time. Based on the resampling results, we suggest optimized acquisition schemes of 13-min duration at 3T and 10-min duration at 7T, whilst retaining low variability (CV ≈ 8%) for the tNAA diffusion measures. Power calculations for the estimation of Dmodel(tNAA) and Davg(tNAA) based on the suggested schemes show that less than 21 subjects per group are

  2. Development of a Multi-Channel, High Frequency QRS Electrocardiograph

    NASA Technical Reports Server (NTRS)

    DePalma, Jude L.

    2003-01-01

    With the advent of the ISS era and the potential requirement for increased cardiovascular monitoring of crewmembers during extended EVAs, NASA flight surgeons would stand to benefit from an evolving technology that allows for a more rapid diagnosis of myocardial ischemia compared to standard electrocardiography. Similarly, during the astronaut selection process, NASA flight surgeons and other physicians would also stand to benefit from a completely noninvasive technology that, either at rest or during maximal exercise tests, is more sensitive than standard ECG in identifying the presence of ischemia. Perhaps most importantly, practicing cardiologists and emergency medicine physicians could greatly benefit from such a device as it could augment (or even replace) standard electrocardiography in settings where the rapid diagnosis of myocardial ischemia (or the lack thereof) is required for proper clinical decision-making. A multi-channel, high-frequency QRS electrocardiograph is currently under development in the Life Sciences Research Laboratories at JSC. Specifically the project consisted of writing software code, some of which contained specially-designed digital filters, which will be incorporated into an existing commercial software program that is already designed to collect, plot and analyze conventional 12-lead ECG signals on a desktop, portable or palm PC. The software will derive the high-frequency QRS signals, which will be analyzed (in numerous ways) and plotted alongside of the conventional ECG signals, giving the PC-viewing clinician advanced diagnostic information that has never been available previously in all 12 ECG leads simultaneously. After the hardware and software for the advanced digital ECG monitor have been fully integrated, plans are to use the monitor to begin clinical studies both on healthy subjects and on patients with known coronary artery disease in both the outpatient and hospital settings. The ultimate goal is to get the technology

  3. Stacked, filtered multi-channel X-ray diode array

    NASA Astrophysics Data System (ADS)

    MacNeil, L. P.; Dutra, E. C.; Compton, S. M.; Jacoby, B. A.; Raphaelian, M. L.

    2015-08-01

    There are many types of X-ray diodes that are used for X-ray flux or spectroscopic measurements and for estimating the spectral shape of the VUV to soft X-ray spectrum. However, a need arose for a low cost, robust X-ray diode to use for experiments in hostile environments on multiple platforms, and for experiments that utilize forces that may destroy the diode(s). Since the typical proposed use required a small size with a minimal single line-of-sight, a parallel array could not be used. So, a stacked, filtered multi-channel X-ray diode array was developed, called the MiniXRD. To achieve significant cost savings while maintaining robustness and ease of field setup, repair, and replacement, we designed the system to be modular. The filters were manufactured in-house and cover the range from 450 eV to 5000 eV. To achieve the line-of-sight accuracy needed, we developed mounts and laser alignment techniques. We modeled and tested elements of the diode design at NSTec Livermore Operations (NSTec / LO) to determine temporal response and dynamic range, leading to diode shape and circuitry changes to optimize impedance and charge storage. We fielded individual and stacked systems at several national facilities as ancillary `ride-along' diagnostics to test and improve the design usability. We present the MiniXRD system performance which supports consideration as a viable low-cost alternative for multiple-channel low-energy X-ray measurements. This diode array is currently at Technical Readiness Level (TRL) 6.

  4. Multichannel polarization stabilization for coherently combined fiber laser arrays.

    PubMed

    Goodno, Gregory D; McNaught, Stuart J; Weber, Mark E; Weiss, S Benjamin

    2012-10-15

    We demonstrate a simplified approach toward active polarization control in coherently combined laser architectures. By leveraging optical phase dithers applied by a phase controller, polarization error signals are generated for an entire laser array from a single beam sample of the combined output, enabling closed-loop polarization locking of non-polarization-maintaining fibers. The concept is shown to be compatible with both hill-climbing and synchronous multidither phase control methods. Simultaneous phase locking and polarization locking was demonstrated for a five-fiber array with >99% phasing efficiency and >20 dB polarization extinction ratio.

  5. Processing of multichannel seismic reflection data acquired in 2013 for seismic investigations of gas hydrates in the Gulf of Mexico

    USGS Publications Warehouse

    Miller, John J.; Agena, Warren F.; Haines, Seth S.; Hart, Patrick E.

    2016-04-13

    As part of a cooperative effort among the U.S. Geological Survey (USGS), the U.S. Department of Energy, and the U.S. Department of the Interior Bureau of Ocean Energy Management, two grids of two-dimensional multichannel seismic reflection data were acquired in the Gulf of Mexico over lease blocks Green Canyon 955 and Walker Ridge 313 between April 18 and May 3, 2013. The purpose of the data acquisition was to fill knowledge gaps in an ongoing study of known gas hydrate accumulations in the area. These data were initially processed onboard the recording ship R/V Pelican for more quality control during the recording. The data were subsequently processed in detail by the U.S. Geological Survey in Denver, Colorado, in two phases. The first phase was to create a “kinematic” dataset that removed extensive noise present in the data but did not preserve relative amplitudes. The second phase was to create a true relative amplitude dataset that included noise removal and “wavelet” deconvolution that preserved the amplitude information. This report describes the processing techniques used to create both datasets.

  6. Recent Progress of the HL-2A Multi-Channel HCOOH Laser Interferometer/Polarimeter

    NASA Astrophysics Data System (ADS)

    Li, Yonggao; Zhou, Yan; Deng, Zhongchao; Li, Yuan; Yi, Jiang; Wang, Haoxi

    2015-05-01

    A multichannel methanoic acid (HCOOH, λ = 432.5 μm) laser interferometer/polarimeter is being developed from the previous eight-channel hydrogen cyanide (HCN, λ = 337 μm) laser interferometer in the HL-2A tokamak. A conventional Michelson-type interometer is used for the electron density measurement, and a Dodel-Kunz-type polarimeter is used for the Faraday rotation effect measurement, respectively. Each HCOOH laser can produce a linearly polarized radiation at a power lever of ˜30 mW, and a power stability <10% in 50 min. A beam waist (diameter d0 ≈12.0 mm, about 200 mm away from the outlet) is finally determined through a chopping modulation technique. The latest optical layout of the interferometer/polarimeter has been finished, and the hardware data processing system based on the fast Fourier transform phase-comparator technique is being explored. In order to demonstrate the feasibility of the diagnostic scheme, two associated bench simulation experiments were carried out in the laboratory, in which the plasma was simulated by a piece of polytetrafluoroethene plate, and the Faraday rotation effect was simulated by a rotating half-wave plate. Simulation results agreed well with the initial experimental conditions. At present, the HCOOH laser interferometer/polarimeter system is being assembled on HL-2A, and is planned to be applied in the 2014-2015 experimental campaign. supported by the National Magnetic Confinement Fusion Science Programs of China (Nos. 2010GB101002 and 2014GB109001), and National Natural Science Foundation of China (Nos. 11075048 and 11275059)

  7. Multi-Channel Seismic Images of the Mariana Forearc: EW0202 Initial Results

    NASA Astrophysics Data System (ADS)

    Oakley, A. J.; Goodliffe, A. M.; Taylor, B.; Moore, G. F.; Fryer, P.

    2002-12-01

    During the Spring of 2002, the Mariana Subduction Factory was surveyed using multi-channel seismics (MCS) as the first major phase of a US-Japanese collaborative NSF-MARGINS funded project. The resulting geophysical transects extend from the Pacific Plate to the West Mariana remnant arc. For details of this survey, including the results from the back-arc, refer to Taylor et al. (this session). The incoming Pacific Plate and its accompanying seamounts are deformed by plate flexure, resulting in extension of the upper crust as it enters the subduction zone. The resultant trench parallel faults dominate the bathymetry and MCS data. Beneath the forearc, in the southern transects near Saipan, the subducting slab is imaged to a distance of 50-60 km arcward. In addition to ubiquitous trench parallel normal faulting, a N-S transect of the forearc clearly shows normal faults perpendicular to the trench resulting from N-S extension. On the east side of the Mariana Ridge, thick sediment packages extend into the forearc. Directly east of Saipan and Tinian, a large, deeply scouring slide mass is imaged. Several serpentine mud volcanoes (Big Blue, Turquoise and Celestial) were imaged on the Mariana Forearc. Deep horizontal reflectors (likely original forearc crust) are imaged under the flanks of some of these seamounts. A possible "throat" reflector is resolved on multiple profiles at the summit of Big Blue, the northern-most seamount in the study area. The flanks of Turquoise seamount terminate in toe thrusts that represent uplift and rotation of surrounding sediments as the volcano grows outward. These thrusts form a basal ridge around the seamount similar to that previously noted encircling Conical Seamount. Furthermore, MCS data has revealed that some forearc highs previously thought to be fault blocks are in actuality mud volcanoes.

  8. [Research on the surface electromyography signal decomposition based on multi-channel signal fusion analysis].

    PubMed

    Li, Qiang; Yang, Jihai

    2012-10-01

    The decomposition method of surface electromyography (sEMG) signals was explored by using the multi-channel information extraction and fusion analysis to acquire the motor unit action potential (MUAP) patterns. The action potential waveforms were detected with the combined method of continuous wavelet transform and hypothesis testing, and the effective detection analysis was judged with the multi-channel firing processes of motor units. The cluster number of MUAPs was confirmed by the hierarchical clustering technique, and then the decomposition was implemented by the fuzzy k-means clustering algorithms. The unclassified waveforms were processed by the template matching and peel-off methods. The experimental results showed that several kinds of MUAPs were precisely extracted from the multi-channel sEMG signals. The space potential distribution information of motor units could be satisfyingly represented by the proposed decomposition method. PMID:23198440

  9. Note: Design and investigation of a multichannel plasma-jet triggered gas switch.

    PubMed

    Tie, Weihao; Liu, Xuandong; Zhang, Qiaogen; Liu, Shanhong

    2014-07-01

    We described the fabrication and testing of a multichannel plasma-jet triggered gas switch (MPJTGS). A novel six-channel annular micro-plasma-gun was embedded in the trigger electrode to generate multichannel plasma jets as a nanosecond trigger pulse arrived. The gas breakdown in multiple sites of the spark gap was induced and fixed around jet orifices by the plasma jets. We tested the multichannel discharge characteristics of the MPJTGS in two working modes with charge voltage of 50 kV, trigger voltage of +40 kV (25 ns rise time), and trigger energy of 240 J, 32 J, and 2 J, respectively, at different working coefficients. Results show that the average number of discharge channels increased as the trigger energy increased, and decreased as the working coefficient decreased. At a working coefficient of 87.1% and trigger energy of 240 J, the average number of discharge channels in Mode II could reach 4.1.

  10. Simultaneous Greedy Analysis Pursuit for compressive sensing of multi-channel ECG signals.

    PubMed

    Avonds, Yurrit; Liu, Yipeng; Van Huffel, Sabine

    2014-01-01

    This paper addresses compressive sensing for multi-channel ECG. Compared to the traditional sparse signal recovery approach which decomposes the signal into the product of a dictionary and a sparse vector, the recently developed cosparse approach exploits sparsity of the product of an analysis matrix and the original signal. We apply the cosparse Greedy Analysis Pursuit (GAP) algorithm for compressive sensing of ECG signals. Moreover, to reduce processing time, classical signal-channel GAP is generalized to the multi-channel GAP algorithm, which simultaneously reconstructs multiple signals with similar support. Numerical experiments show that the proposed method outperforms the classical sparse multi-channel greedy algorithms in terms of accuracy and the single-channel cosparse approach in terms of processing speed.

  11. Overdeepened glacigenic landforms in Lake Thun (Switzerland) revealed by a multichannel reflection seismic survey

    NASA Astrophysics Data System (ADS)

    Fabbri, Stefano; Herwegh, Marco; Schlunegger, Fritz; Hübscher, Christian; Weiss, Benedikt J.; Schmelzbach, Cédric; Horstmeyer, Heinrich; Buechi, Marius W.; Anselmetti, Flavio S.

    2016-04-01

    Recently acquired high-resolution multibeam bathymetry, in combination with a 2D multichannel reflection seismic campaign on perialpine Lake Thun (Switzerland) reveals new insights into the diverse geometry of the lake basin and a so far unknown subaquatic moraine crest with unprecedented clarity. These new data will improve our comprehension concerning the retreat phases of the Aare glacier, the morphology of its proximal deposits and the facies architecture of the subglacial units. The overdeepened basin of Lake Thun was formed by a combination of tectonically predefined weak zones and glacial erosion during the last glacial periods. The new data indicate that below the outermost edge of a morphologically distinct platform in the south eastern part of the lake basin, a ridge structure marked by strong reflection amplitudes occurs. This structure is interpreted as a subaquatic terminal moraine crest, most likely created by a slightly advancing or stagnant grounded Aare glacier during its major retreating phase. The terminal moraine smoothly transforms downstream into well distinguishable foresets with internally recognisable layering, which dip steeply towards the deepest part of the basin, eventually transforming into bottomsets. This depositional sequence formed by the fore- and bottomsets represents ˜50% of the overall sediment volume that fills the basin and was deposited while the glacier was stagnant, interpreted to represent a rather short period of time of a few hundreds of years. This sequence is overlain by lacustrine deposits formed by late-glacial and Holocene laminated muds comprising intercalated turbidites (Wirth et al. 2011). Little is known about the exact timing and behaviour of retreating glaciers between their recessional phase from the Alpine foreland to the deglaciation of the inner-Alpine ice cap, mostly due to the lack of well-developed moraines that indicate glacial stabilization or slight readvance. Findings from pollen analyses by

  12. 7-T magnetic resonance imaging of the inner ear's anatomy by using dual four-element radiofrequency coil arrays and the VIBE sequence

    NASA Astrophysics Data System (ADS)

    Kim, Kyoung-Nam; Heo, Phil; Kim, Young-Bo; Han, Gyu-Cheol

    2015-02-01

    An ultra-high-field magnetic resonance (MR) scanner and a specially-optimized radiofrequency (RF) coil and sequence protocol are required to obtain high-resolution images of the inner ear that can noninvasively confirm pathologic diagnoses. In phantom studies, the MR signal distribution of the gradient echo MR images generated by using a customized RF coil was compared with that of a commercial volume coil. The MR signal intensity of the customized RF coil decreases rapidly from near the RF coil plane toward the exterior of the phantom. However, the signal sensitivity of this coil is superior on both sides of the phantom, corresponding to the petrous pyramid. In in-vivo 7-T MR imaging, a customized RF coil and a volumetric-interpolated breath-hold examination imaging sequence are employed for visualization of the inner ear's structure. The entire membranous portion of the cochlear and the three semicircular canals, including the ductus reunions, oval window, and round window with associated nervous tissue, were clearly depicted with sufficient spatial coverage for adequate inspection of the surrounding anatomy. Developments from a new perspective to inner ear imaging using the 7-T modality could lead to further improved image sensitivity and, thus, enable ultra-structural MR imaging.

  13. Two-voxel spectroscopy with dynamic B0 shimming and flip angle adjustment at 7 T in the human motor cortex.

    PubMed

    Lemke, Clark; Hess, Aaron; Clare, Stuart; Bachtiar, Velicia; Stagg, Charlotte; Jezzard, Peter; Emir, Uzay

    2015-07-01

    The aim of this study was to acquire high-quality in vivo (1) H spectra concurrently from two voxels at ultra-high field (7 T) without specialized hardware. To this end, an acquisition scheme was developed in which first-order shims and flip angles are dynamically updated to acquire spectra from both of the brain's motor cortices in an alternating fashion. To validate this acquisition scheme, separate, static, single-voxel acquisitions were also performed for comparison. Six subjects were examined using semi-LASER spectroscopy at 7 T. Barium titanate pads were used to increase the extent of the effective transmit field (B1 (+) ). Spectra were obtained from the hand area of both motor cortices for both acquisition schemes. LCModel was used to determine neurochemical profiles in order to examine variations between acquisition schemes and volumes of interest. The dynamic two-voxel acquisition protocol produced water linewidths (full width at half-maximum between 11.6 and 12.8 Hz) and signal-to-noise ratios similar to those from static single-voxel measurements. The concentrations of 13 individual and 3 combined metabolites with Cramér-Rao lower bounds below 30% were reliably detected for both acquisition schemes, and agreed well with previous postmortem assay and spectroscopy studies. The results show that high spectral quality from two voxels can be acquired concurrently without specialized hardware. This practical technique can be applied to many neuroscience applications.

  14. [Software development of multi-element transient signal acquisition and processing with multi-channel ICP-AES].

    PubMed

    Zhang, Y; Zhuang, Z; Wang, X; Zhu, E; Liu, J

    2000-02-01

    A software for multi-channel ICP-AES multi-element transient signal acquisition and processing were developed in this paper. It has been successfully applied to signal acquisition and processing in many transient introduction techniques on-line hyphenated with multi-channel ICP-AES.

  15. Multi-Channel Distributed Coordinated Function over Single Radio in Wireless Sensor Networks

    PubMed Central

    Campbell, Carlene E.-A.; Loo, Kok-Keong (Jonathan); Gemikonakli, Orhan; Khan, Shafiullah; Singh, Dhananjay

    2011-01-01

    Multi-channel assignments are becoming the solution of choice to improve performance in single radio for wireless networks. Multi-channel allows wireless networks to assign different channels to different nodes in real-time transmission. In this paper, we propose a new approach, Multi-channel Distributed Coordinated Function (MC-DCF) which takes advantage of multi-channel assignment. The backoff algorithm of the IEEE 802.11 distributed coordination function (DCF) was modified to invoke channel switching, based on threshold criteria in order to improve the overall throughput for wireless sensor networks (WSNs) over 802.11 networks. We presented simulation experiments in order to investigate the characteristics of multi-channel communication in wireless sensor networks using an NS2 platform. Nodes only use a single radio and perform channel switching only after specified threshold is reached. Single radio can only work on one channel at any given time. All nodes initiate constant bit rate streams towards the receiving nodes. In this work, we studied the impact of non-overlapping channels in the 2.4 frequency band on: constant bit rate (CBR) streams, node density, source nodes sending data directly to sink and signal strength by varying distances between the sensor nodes and operating frequencies of the radios with different data rates. We showed that multi-channel enhancement using our proposed algorithm provides significant improvement in terms of throughput, packet delivery ratio and delay. This technique can be considered for WSNs future use in 802.11 networks especially when the IEEE 802.11n becomes popular thereby may prevent the 802.15.4 network from operating effectively in the 2.4 GHz frequency band. PMID:22346614

  16. Network community structure detection for directional neural networks inferred from multichannel multisubject EEG data.

    PubMed

    Liu, Ying; Moser, Jason; Aviyente, Selin

    2014-07-01

    In many neuroscience applications, one is interested in identifying the functional brain modules from multichannel, multiple subject neuroimaging data. However, most of the existing network community structure detection algorithms are limited to single undirected networks and cannot reveal the common community structure for a collection of directed networks. In this paper, we propose a community detection algorithm for weighted asymmetric (directed) networks representing the effective connectivity in the brain. Moreover, the issue of finding a common community structure across subjects is addressed by maximizing the total modularity of the group. Finally, the proposed community detection algorithm is applied to multichannel multisubject electroencephalogram data.

  17. Study on the separation performance of the multi-channel reduced graphene oxide membranes

    NASA Astrophysics Data System (ADS)

    Zhao, Yongjiao; Li, Chun; Fan, Xiaoyan; Wang, Jiesheng; Yuan, Guang; Song, Xinxiang; Chen, Jing; Li, Zhangde

    2016-10-01

    The multi-channel reduced graphene oxide membranes with separation function have been synthesized by a simple hydrothermal reduction method and vacuum filtration. In the as-synthesized membranes, the size, number, and type of the nanochannels can be controlled by the reduced temperature. The flux and retention rate of solution are investigated by filtering different size dye molecules. The interception and adsorption effect in the separation process are discussed. Furthermore, the sizes of the nanochannels in the membranes prepared by the different reduced temperatures are estimated. The results indicate that the multi-channel reduced graphene oxide membranes have potential application in water purification area.

  18. Improving auditory steady-state response detection using independent component analysis on multichannel EEG data.

    PubMed

    Van Dun, Bram; Wouters, Jan; Moonen, Marc

    2007-07-01

    Over the last decade, the detection of auditory steady-state responses (ASSR) has been developed for reliable hearing threshold estimation at audiometric frequencies. Unfortunately, the duration of ASSR measurement can be long, which is unpractical for wide scale clinical application. In this paper, we propose independent component analysis (ICA) as a tool to improve the ASSR detection in recorded single-channel as well as multichannel electroencephalogram (EEG) data. We conclude that ICA is able to reduce measurement duration significantly. For a multichannel implementation, near-optimal performance is obtained with five-channel recordings. PMID:17605353

  19. Optical multichannel recorder and its application in studying a picosecond dye laser

    SciTech Connect

    Vinogradov, S.V.; Kuznetsov, V.V.; Lyutinskii, V.V.; Nazarov, V.N.; Neporent, B.S.; Nikolaev, G.E.; Poznyak, R.I.; Revinskii, V.V.; Sokolov, A.V.; Tovmasyan, S.K.; Chernyavskii, A.F.

    1987-09-01

    The authors created and applied an optical multichannel recorder with a PZS matrix detector for investigating the parameters of laser radiation. The instrument, called on OMR (optical multichannel recorder), records the spatial intensity distribution of a radiation pulse incident on the detector, memorizes it, reproduces it in the form of a semitone map on a television display, and outputs the signal intensity at any point, the intensity distribution over a given cross-section (line), and the integral over the cross section to a digital display.

  20. Fibercore AstroGain fiber: multichannel erbium doped fibers for optical space communications

    NASA Astrophysics Data System (ADS)

    Hill, Mark; Gray, Rebecca; Hankey, Judith; Gillooly, Andy

    2014-03-01

    Fibercore have developed AstroGainTM fiber optimized for multichannel amplifiers used in optical satellite communications and control. The fiber has been designed to take full advantage of the photo-annealing effect that results from pumping in the 980nm region. The proprietary trivalent structure of the core matrix allows optimum recovery following radiation damage to the fiber, whilst also providing a market leading Erbium Doped Fiber Amplifier (EDFA) efficiency. Direct measurements have been taken of amplifier efficiency in a multichannel assembly, which show an effective photo-annealing recovery of up to 100% of the radiation induced attenuation through excitation of point defects.

  1. Multichannel terahertz time-domain spectroscopy system at 1030 nm excitation wavelength.

    PubMed

    Brahm, Anika; Wilms, Annika; Dietz, Roman J B; Göbel, Thorsten; Schell, Martin; Notni, Gunther; Tünnermann, Andreas

    2014-06-01

    We present Terahertz (THz) imaging with a 1D multichannel time-domain spectroscopy (TDS) system which operates with a photoconductive array of 15 detection channels excited by a 1030 nm femtosecond fiber laser. The emitter and detector are photoconductive antennas based on InGaAs/InAlAs multi-layer heterostructures (MLHS). We characterized the THz optics and the resolution of the system. The performance is demonstrated by the multichannel imaging of two samples. A simultaneous measurement of 15 THz pulses with a pixel pitch of 1 mm increases the measurement speed of the TDS system by factor 15. PMID:24921495

  2. Prenatal diagnosis of holoprosencephaly in two fetuses with der (7)t(1;7)(q32;q32)pat inherited from the father with double translocations.

    PubMed

    Chuang, Louise; Kuo, Pao-Lin; Yang, Hsiao-Bai; Chien, Chung-Ho; Chen, Pei-Yi; Chang, Chiung-Hsin; Chang, Fong-Ming

    2003-02-01

    The presence of two independent translocations in one person is rare. Herein, we report the prenatal diagnosis of two sibling fetuses with holoprosencephaly, whose father is a carrier of double translocations. The karyotype of the father is 46,XY, t(1;7) (q32;q32), t(14,15) (q32.1;q26.3). The two fetuses had variable facial dysmorphisms and identical cytogenetic abnormality-a derivative (7) t(1;7) (q32;q32) inherited from the father. The proband 1 showed a small mouth, a single median eye and a proboscis above the eye, while the proband 2 showed hypotelorism, a flat nose, cleft lip and cleft palate. Both fetuses also had alobar holoprosencephaly. Haploinsufficiency of the sonic hedgehog gene at 7q36 does account for the occurrence of holoprosencephaly in the two fetuses with a deletion of distal 7q (7q32 --> qter). PMID:12575020

  3. Sodium Magnetic Resonance Imaging of Ankle Joint in Cadaver Specimens, Volunteers, and Patients After Different Cartilage Repair Techniques at 7 T

    PubMed Central

    Zbýň, Štefan; Brix, Martin O.; Juras, Vladimir; Domayer, Stephan E.; Walzer, Sonja M.; Mlynarik, Vladimir; Apprich, Sebastian; Buckenmaier, Kai; Windhager, Reinhard; Trattnig, Siegfried

    2015-01-01

    Objectives The goal of cartilage repair techniques such as microfracture (MFX) or matrix-associated autologous chondrocyte transplantation (MACT) is to produce repair tissue (RT) with sufficient glycosaminoglycan (GAG) content. Sodium magnetic resonance imaging (MRI) offers a direct and noninvasive evaluation of the GAG content in native cartilage and RT. In the femoral cartilage, this method was able to distinguish between RTs produced by MFX and MACT having different GAG contents. However, it needs to be clarified whether sodium MRI can be useful for evaluating RT in thin ankle cartilage. Thus, the aims of this 7-T study were (1) to validate our sodium MRI protocol in cadaver ankle samples, (2) to evaluate the sodium corrected signal intensities (cSI) in cartilage of volunteers, (3) and to compare sodium values in RT between patients after MFX and MACT treatment. Materials and Methods Five human cadaver ankle samples as well as ankles of 9 asymptomatic volunteers, 6 MFX patients and 6 MACT patients were measured in this 7-T study. Sodium values from the ankle samples were compared with histochemically evaluated GAG content. In the volunteers, sodium cSI values were calculated in the cartilages of ankle and subtalar joint. In the patients, sodium cSI in RT and reference cartilage were measured, morphological appearance of RT was evaluated using the magnetic resonance observation of cartilage repair tissue (MOCART) scoring system, and clinical outcome before and after surgery was assessed using the American Orthopaedic Foot and Ankle Society score and Modified Cincinnati Knee Scale. All regions of interest were defined on morphological images and subsequently transferred to the corresponding sodium images. Analysis of variance, t tests, and Pearson correlation coefficients were evaluated. Results In the patients, significantly lower sodium cSI values were found in RT than in reference cartilage for the MFX (P = 0.007) and MACT patients (P = 0.008). Sodium cSI and

  4. Digital image profilers for detecting faint sources which have bright companions, phase 2

    NASA Technical Reports Server (NTRS)

    Morris, Elena; Flint, Graham

    1991-01-01

    A breadboard image profiling system developed for the first phase of this project demonstrated the potential for detecting extremely faint optical sources in the presence of light companions. Experimental data derived from laboratory testing of the device supports the theory that image profilers of this type may approach the theoretical limit imposed by photon statistics. The objective of Phase 2 of this program is the development of a ground-based multichannel image profiling system capable of detecting faint stellar objects slightly displaced from brighter stars. We have finalized the multichannel image profiling system and attempted three field tests.

  5. Unravelling the complete genome sequence of Advenella mimigardefordensis strain DPN7T and novel insights in the catabolism of the xenobiotic polythioester precursor 3,3'-dithiodipropionate.

    PubMed

    Wübbeler, Jan Hendrik; Hiessl, Sebastian; Schuldes, Jörg; Thürmer, Andrea; Daniel, Rolf; Steinbüchel, Alexander

    2014-07-01

    Advenella mimigardefordensis strain DPN7(T) is a remarkable betaproteobacterium because of its extraordinary ability to use the synthetic disulfide 3,3'-dithiodipropionic acid (DTDP) as the sole carbon source and electron donor for aerobic growth. One application of DTDP is as a precursor substrate for biotechnically synthesized polythioesters (PTEs), which are interesting non-degradable biopolymers applicable for plastics materials. Metabolic engineering for optimization of PTE production requires an understanding of DTDP conversion. The genome of A. mimigardefordensis strain DPN7(T) was sequenced and annotated. The circular chromosome was found to be composed of 4,740,516 bp and 4112 predicted ORFs, whereas the circular plasmid consisted of 23,610 bp and 24 predicted ORFs. The genes participating in DTDP catabolism had been characterized in detail previously, but knowing the complete genome sequence and with support of Tn5: :mob-induced mutants, putatively involved transporter proteins and a transcriptional regulator were also identified. Most probably, DTDP is transported into the cell by a specific tripartite tricarboxylate transport system and is then cleaved by the disulfide reductase LpdA, sulfoxygenated by the 3-mercaptopropionate dioxygenase Mdo, activated by the CoA ligase SucCD and desulfinated by the acyl-CoA dehydrogenase-like desulfinase AcdA. Regulation of this pathway is presumably performed by a transcriptional regulator of the xenobiotic response element family. The excessive sulfate that is inevitably produced is secreted by the cells by a unique sulfate exporter of the CPA (cation : proton antiporter) superfamily.

  6. An experimental study on use of 7T MRI for evaluation of myocardial infarction in SD rats transfected with pcDNA 3.1(+)/VEGF121 plasmid

    PubMed Central

    Zhang, Yan; Tian, Ruiqing; Shen, Xiangchun; Chen, Yushu; Chen, Wei; Gan, Lu; Shen, Guiquan; Ju, Haiyue; Yang, Li; Gao, Fabao

    2016-01-01

    This study aims to build the myocardial infarction model in SD rats transfected with pcDNA 3.1(+)/VEGF121 plasmid and study the effect of the transfection using 7T MRI. Twenty-four male SD rats were randomly divided into 2 groups, pcDNA 3.1(+)/VEGF121 plasmid transfection group (with improved coronary perfusion delivery) and myocardial infarction model group. Cardiac cine magnetic resonance imaging (Cine-MRI), T2-mapping and late gadolinium enhancement (LGE) cardiac imaging were performed at 24 h, 48 h, 72 h and 7 d after myocardial infarction, respectively. The signal intensity, area at risk (AAR), myocardium infarction core (MIC) and salvageable myocardial zone (SMZ) were compared. The hearts were harvested for anatomic characterization, which was related to pathological examination (TTC staining, HE staining, Masson staining and immunohistochemical staining). The Cine-MRI results showed that pcDNA 3.1(+)/VEGF121 plasmid transfection group had higher end-diastolic volume (EDV) with a reduction in MIC and SMZ, as compared with the myocardial infarction model group. MIC, SMZ and AAR of the plasmid transfection declined over time. At 7 d, the two groups did not differ significantly in AAR and T2 value. According to Western Blotting, VEGF was up-regulated, while CaSR and caspase-3 were downregulated in the plasmid transfection group, as compared with the model group. In conclusion, a good treatment effect was achieved by coronary perfusion of pcDNA 3.1(+)/VEGF121 plasmid. 7T CMR sequences provide a non-invasive quantification of the treatment efficacy. However, the assessment of myocardial injury using T2 value and AAR in the presence of edema is less accurate. The myocardial protection of the plasmid transfection group may be related to the inhibition of myocardial apoptosis, vascular endothelial cell (VEC) proliferation and collagen proliferation. The CaSR signaling pathway may contribute to reversing the apoptosis. PMID:27648128

  7. An experimental study on use of 7T MRI for evaluation of myocardial infarction in SD rats transfected with pcDNA 3.1(+)/VEGF121 plasmid.

    PubMed

    Zhang, Yan; Tian, Ruiqing; Shen, Xiangchun; Chen, Yushu; Chen, Wei; Gan, Lu; Shen, Guiquan; Ju, Haiyue; Yang, Li; Gao, Fabao

    2016-01-01

    This study aims to build the myocardial infarction model in SD rats transfected with pcDNA 3.1(+)/VEGF121 plasmid and study the effect of the transfection using 7T MRI. Twenty-four male SD rats were randomly divided into 2 groups, pcDNA 3.1(+)/VEGF121 plasmid transfection group (with improved coronary perfusion delivery) and myocardial infarction model group. Cardiac cine magnetic resonance imaging (Cine-MRI), T2-mapping and late gadolinium enhancement (LGE) cardiac imaging were performed at 24 h, 48 h, 72 h and 7 d after myocardial infarction, respectively. The signal intensity, area at risk (AAR), myocardium infarction core (MIC) and salvageable myocardial zone (SMZ) were compared. The hearts were harvested for anatomic characterization, which was related to pathological examination (TTC staining, HE staining, Masson staining and immunohistochemical staining). The Cine-MRI results showed that pcDNA 3.1(+)/VEGF121 plasmid transfection group had higher end-diastolic volume (EDV) with a reduction in MIC and SMZ, as compared with the myocardial infarction model group. MIC, SMZ and AAR of the plasmid transfection declined over time. At 7 d, the two groups did not differ significantly in AAR and T2 value. According to Western Blotting, VEGF was up-regulated, while CaSR and caspase-3 were downregulated in the plasmid transfection group, as compared with the model group. In conclusion, a good treatment effect was achieved by coronary perfusion of pcDNA 3.1(+)/VEGF121 plasmid. 7T CMR sequences provide a non-invasive quantification of the treatment efficacy. However, the assessment of myocardial injury using T2 value and AAR in the presence of edema is less accurate. The myocardial protection of the plasmid transfection group may be related to the inhibition of myocardial apoptosis, vascular endothelial cell (VEC) proliferation and collagen proliferation. The CaSR signaling pathway may contribute to reversing the apoptosis. PMID:27648128

  8. Differentiating BOLD and non-BOLD signals in fMRI time series from anesthetized rats using multi-echo EPI at 11.7 T.

    PubMed

    Kundu, Prantik; Santin, Mathieu D; Bandettini, Peter A; Bullmore, Edward T; Petiet, Alexandra

    2014-11-15

    The study of spontaneous brain activity using fMRI is central to mapping brain networks. However, current fMRI methodology has limitations in the study of small animal brain organization using ultra-high field fMRI experiments, as imaging artifacts are difficult to control and the relationship between classical neuroanatomy and spontaneous functional BOLD activity is not fully established. Challenges are especially prevalent during the fMRI study of individual rodent brains, which could be instrumental to studies of disease progression and pharmacology. A recent advance in fMRI methodology enables unbiased, accurate, and comprehensive identification of functional BOLD signals by interfacing multi-echo (ME) fMRI acquisition, NMR signal decay analysis, and independent components analysis (ICA), in a procedure called ME-ICA. Here we present a pilot study on the suitability of ME-ICA for ultra high field animal fMRI studies of spontaneous brain activity under anesthesia. ME-ICA applied to 11.7 T fMRI data of rats first showed robust performance in automatic high dimensionality estimation and ICA decomposition, similar to that previously reported for 3.0 T human data. ME sequence optimization for 11.7 T indicated that 3 echoes, 0.5mm isotropic voxel size and TR=3s was adequate for sensitive and specific BOLD signal acquisition. Next, in seeking optimal inhaled isoflurane anesthesia dosage, we report that progressive increase in anesthesia goes with concomitant decrease in statistical complexity of "global" functional activity, as measured by the number of BOLD components, or degrees of freedom (DOF). Finally, BOLD functional connectivity maps for individual rodents at the component level show that spontaneous BOLD activity follows classical neuroanatomy, and seed-based analysis shows plausible cortical-cortical and cortical-subcortical functional interactions.

  9. An experimental study on use of 7T MRI for evaluation of myocardial infarction in SD rats transfected with pcDNA 3.1(+)/VEGF121 plasmid

    PubMed Central

    Zhang, Yan; Tian, Ruiqing; Shen, Xiangchun; Chen, Yushu; Chen, Wei; Gan, Lu; Shen, Guiquan; Ju, Haiyue; Yang, Li; Gao, Fabao

    2016-01-01

    This study aims to build the myocardial infarction model in SD rats transfected with pcDNA 3.1(+)/VEGF121 plasmid and study the effect of the transfection using 7T MRI. Twenty-four male SD rats were randomly divided into 2 groups, pcDNA 3.1(+)/VEGF121 plasmid transfection group (with improved coronary perfusion delivery) and myocardial infarction model group. Cardiac cine magnetic resonance imaging (Cine-MRI), T2-mapping and late gadolinium enhancement (LGE) cardiac imaging were performed at 24 h, 48 h, 72 h and 7 d after myocardial infarction, respectively. The signal intensity, area at risk (AAR), myocardium infarction core (MIC) and salvageable myocardial zone (SMZ) were compared. The hearts were harvested for anatomic characterization, which was related to pathological examination (TTC staining, HE staining, Masson staining and immunohistochemical staining). The Cine-MRI results showed that pcDNA 3.1(+)/VEGF121 plasmid transfection group had higher end-diastolic volume (EDV) with a reduction in MIC and SMZ, as compared with the myocardial infarction model group. MIC, SMZ and AAR of the plasmid transfection declined over time. At 7 d, the two groups did not differ significantly in AAR and T2 value. According to Western Blotting, VEGF was up-regulated, while CaSR and caspase-3 were downregulated in the plasmid transfection group, as compared with the model group. In conclusion, a good treatment effect was achieved by coronary perfusion of pcDNA 3.1(+)/VEGF121 plasmid. 7T CMR sequences provide a non-invasive quantification of the treatment efficacy. However, the assessment of myocardial injury using T2 value and AAR in the presence of edema is less accurate. The myocardial protection of the plasmid transfection group may be related to the inhibition of myocardial apoptosis, vascular endothelial cell (VEC) proliferation and collagen proliferation. The CaSR signaling pathway may contribute to reversing the apoptosis.

  10. Simultaneous multi-slice Turbo-FLASH imaging with CAIPIRINHA for whole brain distortion-free pseudo-continuous arterial spin labeling at 3 and 7 T.

    PubMed

    Wang, Yi; Moeller, Steen; Li, Xiufeng; Vu, An T; Krasileva, Kate; Ugurbil, Kamil; Yacoub, Essa; Wang, Danny J J

    2015-06-01

    Simultaneous multi-slice (SMS) or multiband (MB) imaging has recently been attempted for arterial spin labeled (ASL) perfusion MRI in conjunction with echo-planar imaging (EPI) readout. It was found that SMS-EPI can reduce the T1 relaxation effect of the label and improve image coverage and resolution with little penalty in signal-to-noise ratio (SNR). However, EPI still suffers from geometric distortion and signal dropout from field inhomogeneity effects especially at high and ultrahigh magnetic fields. Here we present a novel scheme for achieving high fidelity distortion-free quantitative perfusion imaging by combining pseudo-continuous ASL (pCASL) with SMS Turbo-FLASH (TFL) readout at both 3 and 7 T. Bloch equation simulation was performed to characterize and optimize the TFL-based pCASL perfusion signal. Two MB factors (3 and 5) were implemented in SMS-TFL pCASL and compared with standard 2D TFL and EPI pCASL sequences. The temporal SNR of SMS-TFL pCASL relative to that of standard TFL pCASL was 0.76 ± 0.10 and 0.74 ± 0.11 at 7 T and 0.70 ± 0.05 and 0.65 ± 0.05 at 3T for MB factor of 3 and 5, respectively. By implementing background suppression in conjunction with SMS-TFL at 3T, the relative temporal SNR improved to 0.84 ± 0.09 and 0.79 ± 0.10 for MB factor of 3 and 5, respectively. Compared to EPI pCASL, significantly increased temporal SNR (p<0.001) and improved visualization of orbitofrontal cortex were achieved using SMS-TFL pCASL. By combining SMS acceleration with TFL pCASL, we demonstrated the feasibility for whole brain distortion-free quantitative mapping of cerebral blood flow at high and ultrahigh magnetic fields.

  11. Multichannel fNIRS Assessment of Overt and Covert Confrontation Naming

    ERIC Educational Resources Information Center

    Moriai-Izawa, Ayano; Dan, Haruka; Dan, Ippeita; Sano, Toshifumi; Oguro, Keiji; Yokota, Hidenori; Tsuzuki, Daisuke; Watanabe, Eiju

    2012-01-01

    Confrontation naming tasks assess cognitive processes involved in the main stage of word production. However, in fMRI, the occurrence of movement artifacts necessitates the use of covert paradigms, which has limited clinical applications. Thus, we explored the feasibility of adopting multichannel functional near-infrared spectroscopy (fNIRS) to…

  12. Self-adaptive method for high frequency multi-channel analysis of surface wave method

    Technology Transfer Automated Retrieval System (TEKTRAN)

    When the high frequency multi-channel analysis of surface waves (MASW) method is conducted to explore soil properties in the vadose zone, existing rules for selecting the near offset and spread lengths cannot satisfy the requirements of planar dominant Rayleigh waves for all frequencies of interest ...

  13. Visual Representation of Eye Gaze Is Coded by a Nonopponent Multichannel System

    ERIC Educational Resources Information Center

    Calder, Andrew J.; Jenkins, Rob; Cassel, Anneli; Clifford, Colin W. G.

    2008-01-01

    To date, there is no functional account of the visual perception of gaze in humans. Previous work has demonstrated that left gaze and right gaze are represented by separate mechanisms. However, these data are consistent with either a multichannel system comprising separate channels for distinct gaze directions (e.g., left, direct, and right) or an…

  14. Consequences of Broad Auditory Filters for Identification of Multichannel-Compressed Vowels

    ERIC Educational Resources Information Center

    Souza, Pamela; Wright, Richard; Bor, Stephanie

    2012-01-01

    Purpose: In view of previous findings (Bor, Souza, & Wright, 2008) that some listeners are more susceptible to spectral changes from multichannel compression (MCC) than others, this study addressed the extent to which differences in effects of MCC were related to differences in auditory filter width. Method: Listeners were recruited in 3 groups:…

  15. Designing Multi-Channel Web Frameworks for Cultural Tourism Applications: The MUSE Case Study.

    ERIC Educational Resources Information Center

    Garzotto, Franca; Salmon, Tullio; Pigozzi, Massimiliano

    A framework for the design of multi-channel (MC) applications in the cultural tourism domain is presented. Several heterogeneous interface devices are supported including location-sensitive mobile units, on-site stationary devices, and personalized CDs that extend the on-site experience beyond the visit time thanks to personal memories gathered…

  16. Comparison of the single channel and multichannel (multivariate) concepts of selectivity in analytical chemistry.

    PubMed

    Dorkó, Zsanett; Verbić, Tatjana; Horvai, George

    2015-07-01

    Different measures of selectivity are in use for single channel and multichannel linear analytical measurements, respectively. It is important to understand that these two measures express related but still distinctly different features of the respective measurements. These relationships are clarified by introducing new arguments. The most widely used selectivity measure of multichannel linear methods (which is based on the net analyte signal, NAS, concept) expresses the sensitivity to random errors of a determination where all bias from interferents is computationally eliminated using pure component spectra. The conventional selectivity measure of single channel linear measurements, on the other hand, helps to estimate the bias caused by an interferent in a biased measurement. In single channel methods expert knowledge about the samples is used to limit the possible range of interferent concentrations. The same kind of expert knowledge allows improved (lower mean squared error, MSE) analyte determinations also in "classical" multichannel measurements if those are intractable due to perfect collinearity or to high noise inflation. To achieve this goal bias variance tradeoff is employed, hence there remains some bias in the results and therefore the concept of single channel selectivity can be extended in a natural way to multichannel measurements. This extended definition and the resulting selectivity measure can also be applied to the so-called inverse multivariate methods like partial least squares regression (PLSR), principal component regression (PCR) and ridge regression (RR). PMID:25882406

  17. Schwinger multichannel study of the 2Pi(g) shape resonance in N2

    NASA Technical Reports Server (NTRS)

    Huo, Winifred M.; Gibson, Thomas L.; Lima, Marco A. P.; Mckoy, Vincent

    1987-01-01

    The results of a study on electron-target correlations in the 2Pi(g) shape resonance of elastic e-N2 scattering, using the Schwinger multichannel formulation, are reported. The effects of basis set, orbital representation, and closed-channel-configurations are delineated. The different roles of radial and angular correlations are compared.

  18. Closed-Loop, Multichannel Experimentation Using the Open-Source NeuroRighter Electrophysiology Platform

    PubMed Central

    Newman, Jonathan P.; Zeller-Townson, Riley; Fong, Ming-Fai; Arcot Desai, Sharanya; Gross, Robert E.; Potter, Steve M.

    2013-01-01

    Single neuron feedback control techniques, such as voltage clamp and dynamic clamp, have enabled numerous advances in our understanding of ion channels, electrochemical signaling, and neural dynamics. Although commercially available multichannel recording and stimulation systems are commonly used for studying neural processing at the network level, they provide little native support for real-time feedback. We developed the open-source NeuroRighter multichannel electrophysiology hardware and software platform for closed-loop multichannel control with a focus on accessibility and low cost. NeuroRighter allows 64 channels of stimulation and recording for around US $10,000, along with the ability to integrate with other software and hardware. Here, we present substantial enhancements to the NeuroRighter platform, including a redesigned desktop application, a new stimulation subsystem allowing arbitrary stimulation patterns, low-latency data servers for accessing data streams, and a new application programming interface (API) for creating closed-loop protocols that can be inserted into NeuroRighter as plugin programs. This greatly simplifies the design of sophisticated real-time experiments without sacrificing the power and speed of a compiled programming language. Here we present a detailed description of NeuroRighter as a stand-alone application, its plugin API, and an extensive set of case studies that highlight the system’s abilities for conducting closed-loop, multichannel interfacing experiments. PMID:23346047

  19. A Multi-Channel Approach for Collaborative Web-Based Learning

    ERIC Educational Resources Information Center

    Azeta, A. A.

    2008-01-01

    This paper describes an architectural framework and a prototype implementation of a web-based multi-channel e-Learning application that allows students, lecturers and the research communities to collaborate irrespective of the communication device a user is carrying. The application was developed based on the concept of "right once run on any…

  20. Comparison of the single channel and multichannel (multivariate) concepts of selectivity in analytical chemistry.

    PubMed

    Dorkó, Zsanett; Verbić, Tatjana; Horvai, George

    2015-07-01

    Different measures of selectivity are in use for single channel and multichannel linear analytical measurements, respectively. It is important to understand that these two measures express related but still distinctly different features of the respective measurements. These relationships are clarified by introducing new arguments. The most widely used selectivity measure of multichannel linear methods (which is based on the net analyte signal, NAS, concept) expresses the sensitivity to random errors of a determination where all bias from interferents is computationally eliminated using pure component spectra. The conventional selectivity measure of single channel linear measurements, on the other hand, helps to estimate the bias caused by an interferent in a biased measurement. In single channel methods expert knowledge about the samples is used to limit the possible range of interferent concentrations. The same kind of expert knowledge allows improved (lower mean squared error, MSE) analyte determinations also in "classical" multichannel measurements if those are intractable due to perfect collinearity or to high noise inflation. To achieve this goal bias variance tradeoff is employed, hence there remains some bias in the results and therefore the concept of single channel selectivity can be extended in a natural way to multichannel measurements. This extended definition and the resulting selectivity measure can also be applied to the so-called inverse multivariate methods like partial least squares regression (PLSR), principal component regression (PCR) and ridge regression (RR).

  1. Diagnostics of physical tautochronism of laser beams in the ISKRA-5 multichannel facility

    SciTech Connect

    Vorontsov, E.N.; Kirdyashkin, M.Yu.; Kravchenko, A.G.

    1994-10-01

    A multichannel system for determining the time parameters of pulsed laser radiation, based on a fast streak camera with fibre-optic communication lines, is described. It is shown that the tautochronism of laser beams can be determined simultaneously in all the channels of the facility and the maximum error does not exceed 25 ps.

  2. The Objective and Subjective Evaluation of Multichannel Expansion in Wide Dynamic Range Compression Hearing Instruments

    ERIC Educational Resources Information Center

    Plyler, Patrick N.; Lowery, Kristy J.; Hamby, Hilary M.; Trine, Timothy D.

    2007-01-01

    Purpose: The effects of multichannel expansion on the objective and subjective evaluation of 20 listeners fitted binaurally with 4-channel, digital in-the-ear hearing instruments were investigated. Method: Objective evaluations were conducted in quiet using the Connected Speech Test (CST) and in noise using the Hearing in Noise Test (HINT) at 40,…

  3. Preparation of uniaxial multichannel silk fibroin scaffolds for guiding primary neurons.

    PubMed

    Zhang, Qiang; Zhao, Yahong; Yan, Shuqin; Yang, Yumin; Zhao, Huijing; Li, Mingzhong; Lu, Shenzhou; Kaplan, David L

    2012-07-01

    Physical guidance cues have been exploited to stimulate neuron adhesion and neurite outgrowth. In the present study, three-dimensional (3-D) silk fibroin scaffolds with uniaxial multichannels (42-142 μm in diameter) were prepared by a directional temperature field freezing technique, followed by lyophilization. By varying the initial silk fibroin concentration, the chemical potential and quantity of free water around cylindrical ice crystals could be controlled to control the cross-section morphology of the scaffold channels. Aligned ridges also formed on the inner surface of the multichannels in parallel to the direction of the channels. In vitro, primary hippocampal neurons were seeded in these 3-D silk fibroin scaffolds with uniaxial multichannels of ∼120 μm in diameter. The morphology of the neurons was multipolar and alignment along the scaffold channels was observed. Cell-cell networks and cell-matrix interactions established by newly formed axons were observed after 7 days in culture. These neurons expressed β-III-tubulin, nerve filament and microtubule-associated protein, while glial fibrillary acidic protein immunofluorescence was barely above background. The ridges on the inner surface of the channels played a critical role in the adhesion and extension of neurons by providing continuous contact guidance. These new 3-D silk scaffolds with uniaxial multichannels provided a favorable microenvironment for the development of hippocampal neurons by guiding axonal elongation and cell migration.

  4. Implementation of the multi-channel monolith reactor in an optimisation procedure for heterogeneous oxidation catalysts based on genetic algorithms.

    PubMed

    Breuer, Christian; Lucas, Martin; Schütze, Frank-Walter; Claus, Peter

    2007-01-01

    A multi-criteria optimisation procedure based on genetic algorithms is carried out in search of advanced heterogeneous catalysts for total oxidation. Simple but flexible software routines have been created to be applied within a search space of more then 150,000 individuals. The general catalyst design includes mono-, bi- and trimetallic compositions assembled out of 49 different metals and depleted on an Al2O3 support in up to nine amount levels. As an efficient tool for high-throughput screening and perfectly matched to the requirements of heterogeneous gas phase catalysis - especially for applications technically run in honeycomb structures - the multi-channel monolith reactor is implemented to evaluate the catalyst performances. Out of a multi-component feed-gas, the conversion rates of carbon monoxide (CO) and a model hydrocarbon (HC) are monitored in parallel. In combination with further restrictions to preparation and pre-treatment a primary screening can be conducted, promising to provide results close to technically applied catalysts. Presented are the resulting performances of the optimisation process for the first catalyst generations and the prospect of its auto-adaptation to specified optimisation goals. PMID:17266517

  5. Influence of paramagnetic melanin on the MRI contrast in melanoma: a combined high-field (11.7 T) MRI and EPR study.

    PubMed

    Godechal, Q; Mignion, L; Karroum, O; Magat, J; Danhier, P; Morandini, R; Ghanem, G E; Leveque, P; Gallez, B

    2014-01-01

    Melanoma is the most dangerous form of skin cancer and its incidence is rising each year. Because the current methods of diagnosis based on the visual aspect of the tumor show limitations, several new techniques are emerging to help in this diagnosis, amongst which are magnetic resonance imaging (MRI) and electron paramagnetic resonance (EPR). The origin of the typical contrast pattern observable in melanoma in T1 - and T2 -weighted images remains to be elucidated and is a source of controversy. In addition, melanin could create sufficient magnetic inhomogeneities to allow its visualization on T2 *-weighted images using high-field MRI. In order to elucidate the possible role of melanin in the MRI contrast of melanoma, the present study was designed to correlate the paramagnetic content in melanin pigment to the contrast on T1 -, T2 - and T2 *-weighted images. MR images were obtained in vivo at 11.7 T using four types of experimental tumors with different pigmentations (B16, HBL, LND1 melanomas and KHT sarcomas). The paramagnetic content in melanin pigment was measured by EPR. No significant correlation was observed between the content in melanin and the relaxation times T1 , T2 and T2 *, emphasizing that the presence of pigment alone has negligible effect on the MRI contrast.

  6. Development of high field SQUID magnetometer for magnetization studies up to 7 T and temperatures in the range from 4.2 to 300 K

    SciTech Connect

    Nagendran, R.; Thirumurugan, N.; Chinnasamy, N.; Janawadkar, M. P.; Sundar, C. S.

    2011-01-15

    We present the design, fabrication, integration, testing, and calibration of a high field superconducting quantum interference device (SQUID) magnetometer. The system is based on dc SQUID sensor with flux locked loop readout electronics. The design is modular and all the subsystems have been fabricated in the form of separate modules in order to simplify the assembly and for ease of maintenance. A novel feature of the system is that the current induced in the pickup loop is distributed as inputs to two different SQUID sensors with different strengths of coupling in order to improve the dynamic range of the system. The SQUID magnetometer has been calibrated with yttrium iron garnet (YIG) sphere as a standard reference material. The calibration factor was determined by fitting the measured flux profile of the YIG sphere to that expected for a point dipole. Gd{sub 2}O{sub 3} was also used as another reference material for the calibration and the effective magnetic moment of the Gd{sup 3+} could be evaluated from the temperature dependent magnetization measurements. The sensitivity of the system has been estimated to be about 10{sup -7} emu at low magnetic fields and about 10{sup -5} emu at high magnetic fields {approx}7 T.

  7. High resolution MRI relaxation measurements of water in the articular cartilage of the meniscectomized rat knee at 4.7 T.

    PubMed

    Spandonis, Yiannis; Heese, Frank P; Hall, Laurance D

    2004-09-01

    Measurements by magnetic resonance imaging (MRI) of the spin-spin (T2), spin-lattice (T1) and spin-density (M0) parameters of water protons, optimized by using the Cramér-Rao Lower Bound (CRLB) theory, were made to quantify the effect of surgically induced osteoarthritis on rat knee cartilage at 4.7 T. Partial meniscectomy was performed on the right medial condyle of four Sprague Dawley rats, leaving the left medial condyle as a control. The animals were euthanized 3 weeks after the operation; the entire limbs were removed and T2 and T1 relaxation measurements and M0 measurements of the protons of water were obtained using conventional Carr-Purcell-Meiboom-Gill (CPMG) and saturation recovery methods. M0 was normalized with respect to a water phantom, to obtain the relative spin-density M0%. Weight-bearing cartilage areas on the meniscectomized medial condyles exhibited a significant increase of T2 relaxation time (p < 0.001) and of M0% (p < 0.01) with respect to the control; T1 relaxation times did not show any statistically significant changes. CRLB-based sampling optimization offered an insight to improved measurement precision and a reduction of scanning time against conventional sampling methods methods. Quantitative MRI assessment of the meniscectomized rat knee shows that cartilage exhibits changes in T2 and M0 values 3 weeks after operation.

  8. Relaxation-compensated CEST-MRI of the human brain at 7T: Unbiased insight into NOE and amide signal changes in human glioblastoma.

    PubMed

    Zaiss, Moritz; Windschuh, Johannes; Paech, Daniel; Meissner, Jan-Eric; Burth, Sina; Schmitt, Benjamin; Kickingereder, Philip; Wiestler, Benedikt; Wick, Wolfgang; Bendszus, Martin; Schlemmer, Heinz-Peter; Ladd, Mark E; Bachert, Peter; Radbruch, Alexander

    2015-05-15

    Endogenous chemical exchange saturation transfer (CEST) effects of protons resonating near to water protons are always diluted by competing effects such as direct water saturation and semi-solid magnetization transfer (MT). This leads to unwanted T2 and MT signal contributions that contaminate the observed CEST signal. Furthermore, all CEST effects appear to be scaled by the T1 relaxation time of the mediating water pool. As MT, T1 and T2 are also altered in tumor regions, a recently published correction algorithm yielding the apparent exchange-dependent relaxation AREX, is used to evaluate in vivo CEST effects. This study focuses on CEST effects of amides (3.5ppm) and Nuclear-Overhauser-mediated saturation transfer (NOE, -3.5ppm) that can be properly isolated at 7T. These were obtained in 10 glioblastoma patients, and this is the first comprehensive study where AREX is applied in human brain as well as in human glioblastoma. The correction of CEST effects alters the contrast significantly: after correction, the CEST effect of amides does not show significant contrast between contrast enhancing tumor regions and normal tissue, whereas NOE drops significantly in the tumor area. In addition, new features in the AREX contrasts are visible. This suggests that previous CEST approaches might not have shown pure CEST effects, but rather water relaxation shine-through effects. Our insights help to improve understanding of the CEST effect changes in tumors and correlations on a cellular and molecular level. PMID:25727379

  9. Ultra-low field T1 vs. T1rho at 3T and 7T: study of rotationally immobilized protein gels and animal brain tissues

    NASA Astrophysics Data System (ADS)

    Dong, Hui; Inglis, Ben; Barr, Ian; Clarke, John

    2015-03-01

    Clinical magnetic resonance imaging (MRI) machines operating in static fields of typically 1.5 T or 3 T can capture information on slow molecular dynamics utilizing the so-called T1rho technique. This technique, in which a radiofrequency (RF) spin-lock field is applied with microtesla amplitude, has been used, for example, to determine the onset time of stroke in studies on rats. The long RF pulse, however, may exceed the specific absorption rate (SAR) limit, putting subjects at risk. Ultra-low-field (ULF) MRI, based on Superconducting Quantum Interference Devices (SQUIDs), directly detects proton signals at a static magnetic field of typically 50-250 μT. Using our ULF MRI system with adjustable static field of typically 55 to 240 μT, we systematically measured the T1 and T2 dispersion profiles of rotationally immobilized protein gels (bovine serum albumin), ex vivo pig brains, and ex vivo rat brains with induced stroke. Comparing the ULF results with T1rho dispersion obtained at 3 T and 7 T, we find that the degree of protein immobilization determines the frequency-dependence of both T1 and T1rho. Furthermore, T1rho and ULF T1 show similar results for stroke, suggesting that ULF MRI may be used to image traumatic brain injury with negligible SAR. This research was supported by the Henry H. Wheeler, Jr. Brain Imaging Center and the Donaldson Trust.

  10. Development of high field SQUID magnetometer for magnetization studies up to 7 T and temperatures in the range from 4.2 to 300 K.

    PubMed

    Nagendran, R; Thirumurugan, N; Chinnasamy, N; Janawadkar, M P; Sundar, C S

    2011-01-01

    We present the design, fabrication, integration, testing, and calibration of a high field superconducting quantum interference device (SQUID) magnetometer. The system is based on dc SQUID sensor with flux locked loop readout electronics. The design is modular and all the subsystems have been fabricated in the form of separate modules in order to simplify the assembly and for ease of maintenance. A novel feature of the system is that the current induced in the pickup loop is distributed as inputs to two different SQUID sensors with different strengths of coupling in order to improve the dynamic range of the system. The SQUID magnetometer has been calibrated with yttrium iron garnet (YIG) sphere as a standard reference material. The calibration factor was determined by fitting the measured flux profile of the YIG sphere to that expected for a point dipole. Gd(2)O(3) was also used as another reference material for the calibration and the effective magnetic moment of the Gd(3+) could be evaluated from the temperature dependent magnetization measurements. The sensitivity of the system has been estimated to be about 10(-7) emu at low magnetic fields and about 10(-5) emu at high magnetic fields ∼7 T.

  11. Surface wave attenuation in the shallow subsurface from multichannel-multishot seismic data: a new approach for detecting fractures and lithological discontinuities

    NASA Astrophysics Data System (ADS)

    Ikeda, Tatsunori; Tsuji, Takeshi

    2016-07-01

    Surface wave analysis generally neglects amplitude information, instead using phase information to delineate near-surface S-wave velocity structures. To effectively characterize subsurface heterogeneities from amplitude information, we propose a method of estimating lateral variation of attenuation coefficients of surface waves from multichannel-multishot (multifold) seismic data. We extend the concept of the common midpoint cross-correlation method, used for phase velocity estimation, to the analysis of attenuation coefficients. Our numerical experiments demonstrated that when used together, attenuation coefficients and phase velocities could characterize a lithological boundary as well as fracture zone. We applied the proposed method to multifold seismic reflection data acquired in Shikoku Island, Japan. We clearly observed abrupt changes in lateral variation of estimated attenuation coefficients around fault locations associated with a lithological boundary and with well-developed fractures, whereas phase velocity results could detect only the lithological boundary. Our study demonstrated that simultaneous interpretation of attenuation coefficients and phase velocities has the potential to distinguish localized fractures from lithological boundaries.

  12. Optimization of a digital lock-in algorithm with a square-wave reference for frequency-divided multi-channel sensor signal detection

    NASA Astrophysics Data System (ADS)

    Zhang, Shengzhao; Li, Gang; Lin, Ling; Zhao, Jing

    2016-08-01

    A digital lock-in detection technique is commonly used to measure the amplitude and phase of a selected frequency signal. A technique that uses a square wave as the reference signal has an advantage over the one using a sinusoidal wave due to its easier implementation and higher computational efficiency. However, demodulating multiple-frequency composite signals using square wave reference may result in interference between channels. To avoid interference between channels and reduce the computational complexity, we modify the calculations and determine the optimal parameter settings of the low-pass filter and carrier frequency, as detailed in this paper. The results of our analysis show that when the length of the average filter and carrier frequencies are properly set, the interference between the channels is removed. This optimization produces the digital lock-in detection suitable for measuring multi-channel sensor signals.

  13. Optimization of a digital lock-in algorithm with a square-wave reference for frequency-divided multi-channel sensor signal detection.

    PubMed

    Zhang, Shengzhao; Li, Gang; Lin, Ling; Zhao, Jing

    2016-08-01

    A digital lock-in detection technique is commonly used to measure the amplitude and phase of a selected frequency signal. A technique that uses a square wave as the reference signal has an advantage over the one using a sinusoidal wave due to its easier implementation and higher computational efficiency. However, demodulating multiple-frequency composite signals using square wave reference may result in interference between channels. To avoid interference between channels and reduce the computational complexity, we modify the calculations and determine the optimal parameter settings of the low-pass filter and carrier frequency, as detailed in this paper. The results of our analysis show that when the length of the average filter and carrier frequencies are properly set, the interference between the channels is removed. This optimization produces the digital lock-in detection suitable for measuring multi-channel sensor signals. PMID:27587155

  14. Optimization of a digital lock-in algorithm with a square-wave reference for frequency-divided multi-channel sensor signal detection.

    PubMed

    Zhang, Shengzhao; Li, Gang; Lin, Ling; Zhao, Jing

    2016-08-01

    A digital lock-in detection technique is commonly used to measure the amplitude and phase of a selected frequency signal. A technique that uses a square wave as the reference signal has an advantage over the one using a sinusoidal wave due to its easier implementation and higher computational efficiency. However, demodulating multiple-frequency composite signals using square wave reference may result in interference between channels. To avoid interference between channels and reduce the computational complexity, we modify the calculations and determine the optimal parameter settings of the low-pass filter and carrier frequency, as detailed in this paper. The results of our analysis show that when the length of the average filter and carrier frequencies are properly set, the interference between the channels is removed. This optimization produces the digital lock-in detection suitable for measuring multi-channel sensor signals.

  15. Characterizing phantom arteries with multi-channel laser ultrasonics and photo-acoustics.

    PubMed

    Johnson, Jami L; van Wijk, Kasper; Sabick, Michelle

    2014-03-01

    Multi-channel photo-acoustic and laser ultrasonic waves are used to sense the characteristics of proxies for healthy and diseased vessels. The acquisition system is non-contacting and non-invasive with a pulsed laser source and a laser vibrometer detector. As the wave signatures of our targets are typically low in amplitude, we exploit multi-channel acquisition and processing techniques. These are commonly used in seismology to improve the signal-to-noise ratio of data. We identify vessel proxies with a diameter on the order of 1 mm, at a depth of 18 mm. Variations in scattered and photo-acoustic signatures are related to differences in vessel wall properties and content. The methods described have the potential to improve imaging and better inform interventions for atherosclerotic vessels, such as the carotid artery. PMID:24412169

  16. A multi-channel high time resolution detector for high content imaging

    NASA Astrophysics Data System (ADS)

    Lapington, J. S.; Fraser, G. W.; Miller, G. M.; Ashton, T. J. R.; Jarron, P.; Despeisse, M.; Powolny, F.; Howorth, J.; Milnes, J.

    2009-10-01

    Medical imaging has long benefited from advances in photon counting detectors arising from space and particle physics. We describe a microchannel plate-based detector system for high content (multi-parametric) analysis, specifically designed to provide a step change in performance and throughput for measurements in imaged live cells and tissue for the 'omics'. The detector system integrates multi-channel, high time resolution, photon counting capability into a single miniaturized detector with integrated ASIC electronics, comprising a fast, low power amplifier discriminator and TDC for every channel of the discrete pixel electronic readout, and achieving a pixel density improvement of order two magnitudes compared with current comparable devices. The device combines high performance, easy reconfigurability, and economy within a compact footprint. We present simulations and preliminary measurements in the context of our ultimate goals of 20 ps time resolution with multi-channel parallel analysis (1024 channels).

  17. Multichannel Speech Enhancement Based on Generalized Gamma Prior Distribution with Its Online Adaptive Estimation

    NASA Astrophysics Data System (ADS)

    Dat, Tran Huy; Takeda, Kazuya; Itakura, Fumitada

    We present a multichannel speech enhancement method based on MAP speech spectral magnitude estimation using a generalized gamma model of speech prior distribution, where the model parameters are adapted from actual noisy speech in a frame-by-frame manner. The utilization of a more general prior distribution with its online adaptive estimation is shown to be effective for speech spectral estimation in noisy environments. Furthermore, the multi-channel information in terms of cross-channel statistics are shown to be useful to better adapt the prior distribution parameters to the actual observation, resulting in better performance of speech enhancement algorithm. We tested the proposed algorithm in an in-car speech database and obtained significant improvements of the speech recognition performance, particularly under non-stationary noise conditions such as music, air-conditioner and open window.

  18. Measurements of alpha-gamma coincidences with an optimized dual-parameter multichannel system.

    PubMed

    Jurado Vargas, M; Caro Marroyo, B; Martín Sánchez, A

    2013-12-01

    Measurements of alpha-gamma coincidences have usually been carried out using a single channel to detect alpha-particles of a given energy, and a multichannel analyser for the detection of the corresponding coincident gamma-rays. An alpha-gamma coincidence chamber coupled to the electronic chain ending with a dual-parameter multichannel analyser has been developed and optimized. This system simultaneously stores alpha-particle, gamma-ray, and alpha-gamma coincidence spectra, which allows a general analysis to be made of the degree of coincidence between each alpha-particle and each gamma-ray emission. With this technique, a two-dimensional spectrum was obtained and analysed using "contour graphics". An application to the study of the decay scheme of (241)Am is described. PMID:24140879

  19. Partial flow compensation by transverse bypass configuration in multi-channel cryogenic compact heat exchanger

    NASA Astrophysics Data System (ADS)

    Jung, Jeheon; Hwang, Gyuwan; Baek, Seungwhan; Jeong, Sangkwon; Rowe, Andrew M.

    2012-01-01

    High-performance multi-channel heat exchangers are vulnerable to small defects such as ill-manufacture or contamination in flow channels. Even slight flow mal-distribution may result in drastic reduction of their thermal performance. In order to accommodate such performance reduction in multi-channel heat exchangers, transverse bypass structure among the channels of hot stream or cold stream is proposed. Since transverse bypass structure enables voluntary flow re-distribution among the channels, detrimental effect of flow defects can be partially reduced and flow mal-distribution can be locally relieved. The lower the flow resistance of transverse bypass is, the more substantial the flow re-distribution is and the larger its effect can be. Quantitative analysis and experimental verification on the effect of transverse bypass is carried out, and the results are presented in this paper.

  20. Towards a multi-channel TOF-PET system with SiPM readout

    NASA Astrophysics Data System (ADS)

    Garutti, Erika; Göttlich, Martin; Harion, Tobias; Hegemann, Niklas; Schmidt, Maximilian; Schultz-Coulon, Hans-Christian; Shen, Wei; Silenzi, Alessandro; Stamen, Rainer; Tadday, Alexander; Xu, Chen

    2012-12-01

    The goal of this project is to develop a multi-channel TOF-PET system with a 300 ps FWHM time resolution, a factor two improvement with respect to commercially available systems (Surti et al., 2007 [1]). In a TOF-PET system, the time-of-flight information can be used to improve significantly the sensitivity of the detector as shown in Karp et al. (2008) [2]. The target time resolution has been achieved in two channel systems with LYSO (Kim and Wang, 2008 [3]), the aim is to port this results into a multi-channel system. This work extends the results shown in Göttlich et al. (2010) [4], studying the stability of the detector performance in different geometries and configurations.

  1. Characterizing phantom arteries with multi-channel laser ultrasonics and photo-acoustics.

    PubMed

    Johnson, Jami L; van Wijk, Kasper; Sabick, Michelle

    2014-03-01

    Multi-channel photo-acoustic and laser ultrasonic waves are used to sense the characteristics of proxies for healthy and diseased vessels. The acquisition system is non-contacting and non-invasive with a pulsed laser source and a laser vibrometer detector. As the wave signatures of our targets are typically low in amplitude, we exploit multi-channel acquisition and processing techniques. These are commonly used in seismology to improve the signal-to-noise ratio of data. We identify vessel proxies with a diameter on the order of 1 mm, at a depth of 18 mm. Variations in scattered and photo-acoustic signatures are related to differences in vessel wall properties and content. The methods described have the potential to improve imaging and better inform interventions for atherosclerotic vessels, such as the carotid artery.

  2. Testing and Performance Analysis of the Multichannel Error Correction Code Decoder

    NASA Technical Reports Server (NTRS)

    Soni, Nitin J.

    1996-01-01

    This report provides the test results and performance analysis of the multichannel error correction code decoder (MED) system for a regenerative satellite with asynchronous, frequency-division multiple access (FDMA) uplink channels. It discusses the system performance relative to various critical parameters: the coding length, data pattern, unique word value, unique word threshold, and adjacent-channel interference. Testing was performed under laboratory conditions and used a computer control interface with specifically developed control software to vary these parameters. Needed technologies - the high-speed Bose Chaudhuri-Hocquenghem (BCH) codec from Harris Corporation and the TRW multichannel demultiplexer/demodulator (MCDD) - were fully integrated into the mesh very small aperture terminal (VSAT) onboard processing architecture and were demonstrated.

  3. Waveform analysis with optical multichannel detectors: Applications for rapid-scan spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    An, Ilsin; Collins, R. W.

    1991-08-01

    A unique rapid-scanning ellipsometer employing a rotating polarizer optical configuration and a multichannel detector for a 1.5-4.5 eV spectral range, has been developed recently for real time studies of film growth and surfaces. This is a new application of the photodiode array-based optical multichannel detector that entails waveform analysis of the incident irradiance at each photon energy. For accurate ellipsometric spectra {ψ(hν),Δ(hν)}, the raw data in the form of photon counts, integrated over four or more equal sectors of polarizer rotation, must be corrected for systematic errors originating from the detection system. Simple procedures are described to characterize and correct for the most significant errors including detection system nonlinearity, image persistence, and scattered stray light in the spectrograph/detector enclosure.

  4. Detecting missing signals in multichannel recordings by using higher order statistics.

    PubMed

    Halabi, R; Diab, M O; Moslem, B; Khalil, M; Marque, C

    2012-01-01

    In real world applications, a multichannel acquisition system is susceptible of having one or many of its sensors displaced or detached, leading therefore to the loss or corruption of the recorded signals. In this paper, we present a technique for detecting missing or corrupted signals in multichannel recordings. Our approach is based on Higher Order Statistics (HOS) analysis. Our approach is tested on real uterine electromyogram (EMG) signals recorded by 4×4 electrode grid. Results have shown that HOS descriptors can discriminate between the two classes of signals (missing vs. non-missing). These results are supported by statistical analysis using the t-test which indicated good statistical significance of 95% confidence level.

  5. Removing artifacts and background activity in multichannel electroencephalograms by enhancing common activity.

    PubMed

    De Clercq, Wim; Van Paesschen, Wim; Vanrumste, Bart; Papy, J-M; Vergult, Anneleen; Van Huffel, Sabine

    2005-01-01

    Removing artifacts and background EEG from multichannel interictal and ictal EEG has become a major research topic in EEG signal processing in recent years. We applied for this purpose a recently developed subspace-based method for modelling the common dynamics in multichannel signals. When the epileptiform activity is common in the majority of channels and the artifacts appear only in a few channels the proposed method can be used to remove the latter. The performance of the method was tested on simulated data for different noise levels. For high noise levels the method was still able to identify the common dynamics. In addition, the method was applied to a real life EEG recording. Also in this case the muscle artifacts were removed successfully. For both the synthetic data and the analyzed real life data the results were compared with the results obtained with principal component analysis (PCA). In both cases the proposed method performed better than PCA.

  6. Modeling common dynamics in multichannel signals with applications to artifact and background removal in EEG recordings.

    PubMed

    De Clercq, Wim; Vanrumste, Bart; Papy, Jean-Michel; Van Paesschen, Wim; Van Huffel, Sabine

    2005-12-01

    Removing artifacts and background electroencephaloraphy (EEG) from multichannel interictal and ictal EEG has become a major research topic in EEG signal processing in recent years. We applied for this purpose a recently developed subspace-based method for modeling the common dynamics in multichannel signals. When the epileptiform activity is common in the majority of channels and the artifacts appear only in a few channels the proposed method can be used to remove the latter. The performance of the method was tested on simulated data for different noise levels. For high noise levels the method was still able to identify the common dynamics. In addition, the method was applied to real life EEG recordings containing interictal and ictal activity contaminated with muscle artifact. The muscle artifacts were removed successfully. For both the synthetic data and the analyzed real life data the results were compared with the results obtained with principal component analysis (PCA). In both cases, the proposed method performed better than PCA.

  7. Tunability of multichannel optical filter based on magnetized one-dimensional plasma photonic crystal

    SciTech Connect

    Jamshidi-Ghaleh, K. Karami-Garehgeshlagi, F.; Mazloom, A. A.

    2015-10-15

    A one dimensional plasma photonic crystal (1DPPC) structure was proposed to design a tunable compressing/broadening multi-channel optical filter with external controllability. The 1DPPC with arrangement of (AP){sup n}D(PA){sup n}, where A and D are the dielectric materials, P is a magnetized plasma layer and n is the number of the periodicity, was proposed. The well-known transfer matrix method was employed for analysis. In linear transmittance spectrum, n − 1 defect modes were appeared inside the photonic band gap. The results were shown that by increasing the applied magnetic field intensity and its direction, a red-shift and blue-shift were, respectively, observed in defect mode frequencies. On the other hand, the modes were compressed and broadened with increasing the intensity and the direction of the applied magnetic field, respectively. Externally controllable defect modes can be useful in designing a multichannel tunable optical filter.

  8. Multichannel system based on a high sensitivity superconductive sensor for magnetoencephalography.

    PubMed

    Rombetto, Sara; Granata, Carmine; Vettoliere, Antonio; Russo, Maurizio

    2014-07-08

    We developed a multichannel system based on superconducting quantum interference devices (SQUIDs) for magnetoencephalography measurements. Our system consists of 163 fully-integrated SQUID magnetometers, 154 channels and 9 references, and all of the operations are performed inside a magnetically-shielded room. The system exhibits a magnetic field noise spectral density of approximatively 5 fT/Hz(1=2). The presented magnetoencephalography is the first system working in a clinical environment in Italy.

  9. Multichannel active noise control system for local spectral reshaping of multifrequency noise

    NASA Astrophysics Data System (ADS)

    de Diego, M.; Gonzalez, A.; Ferrer, M.; Piñero, G.

    2004-07-01

    This paper discusses the development of a multichannel active system for local spectral reshaping of multitone noise. The aim of this work is to design a real practical system that performs well in local active noise control (ANC) applications, and so improving the comfort sensation produced by enclosed sound fields. The adaptive algorithm implemented in the controller is a multichannel extension of the multifrequency adaptive equalizer developed by Kuo. The philosophy behind these equalizers lies in independently controlling some given frequencies of a primary signal. Moreover, the algorithm should manage to generate usefully sized zones of equalization in order to allow for the head motion of somebody with restricted mobility; for example, a passenger seated in a car. To verify the successful implementation of the multichannel system, experiments were carried out under listening room conditions. The developed prototype consists of an array of up to four microphones used as error sensors and two secondary sources. A 4100-type Bruel and Kjaer mannequin with two calibrated microphones at the ear canals was used to measure sound levels in a hypothetical listener's head. Different synthesized repetitive noises were used, as reference signals, specifically repetitive noise with harmonics of 15, 20, and 28 Hz, as well as an 80 Hz single tone. The equalized points include an area around the error sensor positions, and these are measured using the mannequin and an x- y moving platform. The extent to which the experimental equalization zones obtained favourable results validates the multichannel local ANC equalization system. Different error sensor positions around the listener head were also tested. The residual field inside the equalization zone was measured in all cases.

  10. Avian embryo monitoring during incubation using multi-channel diffuse speckle contrast analysis.

    PubMed

    Yeo, Chaebeom; Park, Hyun-Cheol; Lee, Kijoon; Song, Cheol

    2016-01-01

    Determining the survival rate of avian embryos during incubation is essential for cost-saving in the poultry industry. A multi-channel diffuse speckle contrast analysis (DSCA) system, comprising four optical fiber channels, is proposed to achieve noninvasive in vivo measurements of deep tissue flow. The system was able to monitor chick embryo vital signs over the entire incubation period. Moreover, it proved useful in distinguishing between chick embryos in healthy and weakened conditions. PMID:26819820

  11. [Use of multichannel programmed electrostimulation for the rehabilitation of patients with multiple sclerosis].

    PubMed

    Popova, N F; Shagaev, A S

    2009-01-01

    Ninety-eight patients with definite multiple sclerosis (MS) have been examined. An effect of functional multichannel programmed electrostimulation (FMPES) on the restoration of balance and biomechanics of walking of patients with different types of MS and severity of neurological deficit was estimated. The effectiveness was measured with stabilometric analysis. The method was efficient in patients with mild and moderate degree of neurological deficit severity. Recommendations on the use of FMPES for patients with different disease severity are formulated.

  12. IPOD-USGS multichannel seismic reflection profile from Cape Hatteras to the Mid-Atlantic Ridge

    USGS Publications Warehouse

    Grow, John A.; Markl, Rudi G.

    1977-01-01

    A 3,400-km-long multichannel seismic-reflection profile from Cape Hatteras to the Mid-Atlantic Ridge was acquired commercially under contract to the National Science Foundation and the U.S. Geological Survey. These data show evidence for massive erosion of the continental slope, diapirs at the base of the continental slope, and mantle reflections beneath the Hatteras Abyssal Plain.

  13. Fabry-Pérot-multichannel spectrometer tandem for ultra-high resolution Raman spectroscopy.

    PubMed

    Rozas, Guillermo; Jusserand, Bernard; Fainstein, Alejandro

    2014-01-01

    We present a novel ultra-high resolution Raman spectroscopy technique based in a Fabry-Pérot/triple spectrometer tandem with multichannel acquisition. We describe the system, detail the calibration process, and experimentally test the technique, showing that effective finesses in excess of 1000 are possible. The technique is specifically tailored for low intensity, complex and spectrally extended Raman spectra, providing shorter acquisition times with respect to similar tandem systems with monochannel detectors.

  14. Multichannel heterodyne radiometer with computer control for electron cyclotron emission measurements of a tokomak plasma

    SciTech Connect

    Cima, G.; Ramponi, G.; Simonetto, A.

    1985-10-01

    A multichannel heterodyne radiometer in the frequency range 50--75 GHz which has been used to measure the second-harmonic cyclotron emission of the Thor Tokomak plasma is described. Real-time frequency switching, analog output averaging, autocalibration, data-acquisition, and graphical display are all functions performed under control of an Apple II personal computer. Typical experimental results are presented to illustrate the measuring capabilities of the instrument.

  15. Multichannel heterodyne radiometer with computer control for electron cyclotron emission measurements of a tokamak plasma

    NASA Astrophysics Data System (ADS)

    Cima, G.; Ramponi, G.; Simonetto, A.

    1985-10-01

    A multichannel heterodyne radiometer in the frequency range 50-75 GHz which has been used to measure the second-harmonic cyclotron emission of the Thor Tokomak plasma is described. Real-time frequency switching, analog output averaging, autocalibration, data-acquisition, and graphical display are all functions performed under control of an Apple II personal computer. Typical experimental results are presented to illustrate the measuring capabilities of the instrument.

  16. Bayesian experimental design of a multichannel interferometer for Wendelstein 7-Xa)

    NASA Astrophysics Data System (ADS)

    Dreier, H.; Dinklage, A.; Fischer, R.; Hirsch, M.; Kornejew, P.

    2008-10-01

    Bayesian experimental design (BED) is a framework for the optimization of diagnostics basing on probability theory. In this work it is applied to the design of a multichannel interferometer at the Wendelstein 7-X stellarator experiment. BED offers the possibility to compare diverse designs quantitatively, which will be shown for beam-line designs resulting from different plasma configurations. The applicability of this method is discussed with respect to its computational effort.

  17. Avian embryo monitoring during incubation using multi-channel diffuse speckle contrast analysis

    PubMed Central

    Yeo, Chaebeom; Park, Hyun-cheol; Lee, Kijoon; Song, Cheol

    2015-01-01

    Determining the survival rate of avian embryos during incubation is essential for cost-saving in the poultry industry. A multi-channel diffuse speckle contrast analysis (DSCA) system, comprising four optical fiber channels, is proposed to achieve noninvasive in vivo measurements of deep tissue flow. The system was able to monitor chick embryo vital signs over the entire incubation period. Moreover, it proved useful in distinguishing between chick embryos in healthy and weakened conditions. PMID:26819820

  18. 3D superalloy grain segmentation using a multichannel edge-weighted centroidal Voronoi tessellation algorithm.

    PubMed

    Cao, Yu; Ju, Lili; Zhou, Youjie; Wang, Song

    2013-10-01

    Accurate grain segmentation on 3D superalloy images is very important in materials science and engineering. From grain segmentation, we can derive the underlying superalloy grains' micro-structures, based on how many important physical, mechanical, and chemical properties of the superalloy samples can be evaluated. Grain segmentation is, however, usually a very challenging problem because: 1) even a small 3D superalloy sample may contain hundreds of grains; 2) carbides and noises may degrade the imaging quality; and 3) the intensity within a grain may not be homogeneous. In addition, the same grain may present different appearances, e.g., different intensities, under different microscope settings. In practice, a 3D superalloy image may contain multichannel information where each channel corresponds to a specific microscope setting. In this paper, we develop a multichannel edge-weighted centroidal Voronoi tessellation (MCEWCVT) algorithm to effectively and robustly segment the superalloy grains from 3D multichannel superalloy images. MCEWCVT performs segmentation by minimizing an energy function, which encodes both the multichannel voxel-intensity similarity within each cluster in the intensity domain and the smoothness of segmentation boundaries in the 3D image domain. In the experiment, we first quantitatively evaluate the proposed MCEWCVT algorithm on a four-channel Ni-based 3D superalloy data set (IN100) against the manually annotated ground-truth segmentation. We further evaluate the MCEWCVT algorithm on two synthesized four-channel superalloy data sets. The qualitative and quantitative comparisons of 18 existing image segmentation algorithms demonstrate the effectiveness and robustness of the proposed MCEWCVT algorithm. PMID:23797261

  19. [Design and Implementation of the Multi-Channel Meridian Impedance Detector Based on Current Driving].

    PubMed

    Cao, Chenghu; Chen, Xin

    2015-03-01

    A multi-channel meridian impedance detector used to the 3D meridian visualization positioning is presented. The detector is designed with the four-electrode method based on current driving according to low impedance of the meridian. The detector consists of power-supply module, sinusoidal signal generator, voltage-controlled current source, isolation amplifiers, filter circuit, amplitude detectors and so on. PMID:26204737

  20. Optical multichannel room temperature magnetic field imaging system for clinical application

    PubMed Central

    Lembke, G.; Erné, S. N.; Nowak, H.; Menhorn, B.; Pasquarelli, A.

    2014-01-01

    Optically pumped magnetometers (OPM) are a very promising alternative to the superconducting quantum interference devices (SQUIDs) used nowadays for Magnetic Field Imaging (MFI), a new method of diagnosis based on the measurement of the magnetic field of the human heart. We present a first measurement combining a multichannel OPM-sensor with an existing MFI-system resulting in a fully functional room temperature MFI-system. PMID:24688820

  1. Multichannel heterodyning for wideband interferometry, correlation and signal processing

    DOEpatents

    Erskine, D.J.

    1999-08-24

    A method is disclosed of signal processing a high bandwidth signal by coherently subdividing it into many narrow bandwidth channels which are individually processed at lower frequencies in a parallel manner. Autocorrelation and correlations can be performed using reference frequencies which may drift slowly with time, reducing cost of device. Coordinated adjustment of channel phases alters temporal and spectral behavior of net signal process more precisely than a channel used individually. This is a method of implementing precision long coherent delays, interferometers, and filters for high bandwidth optical or microwave signals using low bandwidth electronics. High bandwidth signals can be recorded, mathematically manipulated, and synthesized. 50 figs.

  2. Multichannel heterodyning for wideband interferometry, correlation and signal processing

    DOEpatents

    Erskine, David J.

    1999-01-01

    A method of signal processing a high bandwidth signal by coherently subdividing it into many narrow bandwidth channels which are individually processed at lower frequencies in a parallel manner. Autocorrelation and correlations can be performed using reference frequencies which may drift slowly with time, reducing cost of device. Coordinated adjustment of channel phases alters temporal and spectral behavior of net signal process more precisely than a channel used individually. This is a method of implementing precision long coherent delays, interferometers, and filters for high bandwidth optical or microwave signals using low bandwidth electronics. High bandwidth signals can be recorded, mathematically manipulated, and synthesized.

  3. Processing and Analysis of Multichannel Extracellular Neuronal Signals: State-of-the-Art and Challenges

    PubMed Central

    Mahmud, Mufti; Vassanelli, Stefano

    2016-01-01

    In recent years multichannel neuronal signal acquisition systems have allowed scientists to focus on research questions which were otherwise impossible. They act as a powerful means to study brain (dys)functions in in-vivo and in in-vitro animal models. Typically, each session of electrophysiological experiments with multichannel data acquisition systems generate large amount of raw data. For example, a 128 channel signal acquisition system with 16 bits A/D conversion and 20 kHz sampling rate will generate approximately 17 GB data per hour (uncompressed). This poses an important and challenging problem of inferring conclusions from the large amounts of acquired data. Thus, automated signal processing and analysis tools are becoming a key component in neuroscience research, facilitating extraction of relevant information from neuronal recordings in a reasonable time. The purpose of this review is to introduce the reader to the current state-of-the-art of open-source packages for (semi)automated processing and analysis of multichannel extracellular neuronal signals (i.e., neuronal spikes, local field potentials, electroencephalogram, etc.), and the existing Neuroinformatics infrastructure for tool and data sharing. The review is concluded by pinpointing some major challenges that are being faced, which include the development of novel benchmarking techniques, cloud-based distributed processing and analysis tools, as well as defining novel means to share and standardize data. PMID:27313507

  4. Alternative construction of interleaved RLL codes for partial response channels using multichannel methods

    NASA Astrophysics Data System (ADS)

    Swanson, Robert E.

    1994-09-01

    Current work in magnetic recording channels has demonstrated significant improvement in recording density using partial response communication methods along with maximum likelihood detection. The class IV partial response channel (PR4) behaves as the interleaving of two identical run-length limited (RLL) channels. Efficient recording codes for the PR4 channel have been made by considering a channel bit sequence to be composed of two interleaved subsequences. Finite state techniques are used to describe run-length constraints on each subsequence as well as a global run-length constraint on both sequences combined. A recent paper by Swanson and Wolf discusses multichannel run-length limited codes that turn out to be very similar to interleaved run-length limited codes. The present paper discusses the similarities between the code description of multichannel RLL codes and the interleaved RLL codes required by the PR4 channel. The extension of the techniques of multichannel RLL work to the interleaved problem is discussed. It was found that suitable code constructions are possible by viewing the problem as two distinct RLL codes that have individual maximum run-lengths onto which a global run-length is imposed. Two examples are developed to illustrate the ideas.

  5. A Multichannel Dampened Flow System for Studies on Shear Stress-Mediated Mechanotransduction

    PubMed Central

    Voyvodic, Peter L.; Min, Daniel; Baker, Aaron B.

    2012-01-01

    Shear stresses are powerful regulators of cellular function and potent mediators of the development of vascular disease. We have designed and optimized a system allowing the application of flow to cultured cells in a multichannel format. By using a multichannel peristaltic pump, flow can be driven continuously in the system for long-term studies in multiple isolated flow loops. A key component of the system is a dual-chamber pulse dampener that removes the pulsatility of the flow without the need for having an open system or elevated reservoir. We optimized the design parameters of the pulse dampening chambers for the maximum reduction in flow pulsation while minimizing the fluid needed for each isolated flow channel. Human umbilical vein endothelial cells (HUVECs) were exposed to steady and pulsatile shear stress using the system. We found that cells under steady flow had a marked increased production of eNOS and formation of actin stress fibers in comparison to those under pulsatile flow conditions. Overall, the results confirm the utility of the device as a practical means to apply shear stress to cultured cells in the multichannel format and provide steady, long term flow to microfluidic devices. PMID:22836694

  6. A multichannel dampened flow system for studies on shear stress-mediated mechanotransduction.

    PubMed

    Voyvodic, Peter L; Min, Daniel; Baker, Aaron B

    2012-09-21

    Shear stresses are powerful regulators of cellular function and potent mediators of the development of vascular disease. We have designed and optimized a system allowing the application of flow to cultured cells in a multichannel format. By using a multichannel peristaltic pump, flow can be driven continuously in the system for long-term studies in multiple isolated flow loops. A key component of the system is a dual-chamber pulse dampener that removes the pulsatility of the flow without the need for having an open system or elevated reservoir. We optimized the design parameters of the pulse dampening chambers for the maximum reduction in flow pulsation while minimizing the fluid needed for each isolated flow channel. Human umbilical vein endothelial cells (HUVECs) were exposed to steady and pulsatile shear stress using the system. We found that cells under steady flow had a marked increased production of eNOS and formation of actin stress fibers in comparison to those under pulsatile flow conditions. Overall, the results confirm the utility of the device as a practical means to apply shear stress to cultured cells in the multichannel format and provide steady, long term flow to microfluidic devices.

  7. Initiation techniques and the vacuum-ultraviolet-radiation efficiency of a stabilized multichannel surface discharge

    NASA Astrophysics Data System (ADS)

    Tcheremiskine, V. I.; Uteza, O. P.; Sentis, M. L.; Mikheev, L. D.

    2006-01-01

    Multichannel surface discharges possess a number of advantageous characteristics for the optical pumping of photochemically driven lasers. This work reports on a type of large-area low-inductance sources of intense UV-VUV (vacuum-ultraviolet) radiation based on spatially stabilized multichannel discharges in gases. The discharges consist of several dozens of closely located parallel plasma channels initiated synchronously along a dielectric surface on the area of several hundred square centimeters. In comparison with a large-area diffuse surface discharge, the plasma confinement within relatively thin channels greatly improves the efficiency of the discharge emission in the VUV spectral range. Several techniques are introduced, which allow a synchronous formation and homogeneous development of multiple spatially stabilized discharge channels. Technical efficiency of the discharge radiation within the spectral range of 120-200nm reaches 5% and an effective brightness temperature of the radiating plasma exceeds 20kK. Synchronous operation of a number of multichannel discharge modules producing high-intensity submicrosecond optical pulses is demonstrated, which is of importance for the pump source scaling and geometrical adaptation.

  8. The algorithmic complexity of multichannel EEGs is sensitive to changes in behavior.

    PubMed

    Watanabe, T A A; Cellucci, C J; Kohegyi, E; Bashore, T R; Josiassen, R C; Greenbaun, N N; Rapp, P E

    2003-01-01

    Symbolic measures of complexity provide a quantitative characterization of the sequential structure of symbol sequences. Promising results from the application of these methods to the analysis of electroencephalographic (EEG) and event-related brain potential (ERP) activity have been reported. Symbolic measures used thus far have two limitations, however. First, because the value of complexity increases with the length of the message, it is difficult to compare signals of different epoch lengths. Second, these symbolic measures do not generalize easily to the multichannel case. We address these issues in studies in which both single and multichannel EEGs were analyzed using measures of signal complexity and algorithmic redundancy, the latter being defined as a sequence-sensitive generalization of Shannon's redundancy. Using a binary partition of EEG activity about the median, redundancy was shown to be insensitive to the size of the data set while being sensitive to changes in the subject's behavioral state (eyes open vs. eyes closed). The covariance complexity, calculated from the singular value spectrum of a multichannel signal, was also found to be sensitive to changes in behavioral state. Statistical separations between the eyes open and eyes closed conditions were found to decrease following removal of the 8- to 12-Hz content in the EEG, but still remained statistically significant. Use of symbolic measures in multivariate signal classification is described.

  9. Content-Based Multi-Channel Network Coding Algorithm in the Millimeter-Wave Sensor Network

    PubMed Central

    Lin, Kai; Wang, Di; Hu, Long

    2016-01-01

    With the development of wireless technology, the widespread use of 5G is already an irreversible trend, and millimeter-wave sensor networks are becoming more and more common. However, due to the high degree of complexity and bandwidth bottlenecks, the millimeter-wave sensor network still faces numerous problems. In this paper, we propose a novel content-based multi-channel network coding algorithm, which uses the functions of data fusion, multi-channel and network coding to improve the data transmission; the algorithm is referred to as content-based multi-channel network coding (CMNC). The CMNC algorithm provides a fusion-driven model based on the Dempster-Shafer (D-S) evidence theory to classify the sensor nodes into different classes according to the data content. By using the result of the classification, the CMNC algorithm also provides the channel assignment strategy and uses network coding to further improve the quality of data transmission in the millimeter-wave sensor network. Extensive simulations are carried out and compared to other methods. Our simulation results show that the proposed CMNC algorithm can effectively improve the quality of data transmission and has better performance than the compared methods. PMID:27376302

  10. Content-Based Multi-Channel Network Coding Algorithm in the Millimeter-Wave Sensor Network.

    PubMed

    Lin, Kai; Wang, Di; Hu, Long

    2016-01-01

    With the development of wireless technology, the widespread use of 5G is already an irreversible trend, and millimeter-wave sensor networks are becoming more and more common. However, due to the high degree of complexity and bandwidth bottlenecks, the millimeter-wave sensor network still faces numerous problems. In this paper, we propose a novel content-based multi-channel network coding algorithm, which uses the functions of data fusion, multi-channel and network coding to improve the data transmission; the algorithm is referred to as content-based multi-channel network coding (CMNC). The CMNC algorithm provides a fusion-driven model based on the Dempster-Shafer (D-S) evidence theory to classify the sensor nodes into different classes according to the data content. By using the result of the classification, the CMNC algorithm also provides the channel assignment strategy and uses network coding to further improve the quality of data transmission in the millimeter-wave sensor network. Extensive simulations are carried out and compared to other methods. Our simulation results show that the proposed CMNC algorithm can effectively improve the quality of data transmission and has better performance than the compared methods. PMID:27376302

  11. Processing and Analysis of Multichannel Extracellular Neuronal Signals: State-of-the-Art and Challenges.

    PubMed

    Mahmud, Mufti; Vassanelli, Stefano

    2016-01-01

    In recent years multichannel neuronal signal acquisition systems have allowed scientists to focus on research questions which were otherwise impossible. They act as a powerful means to study brain (dys)functions in in-vivo and in in-vitro animal models. Typically, each session of electrophysiological experiments with multichannel data acquisition systems generate large amount of raw data. For example, a 128 channel signal acquisition system with 16 bits A/D conversion and 20 kHz sampling rate will generate approximately 17 GB data per hour (uncompressed). This poses an important and challenging problem of inferring conclusions from the large amounts of acquired data. Thus, automated signal processing and analysis tools are becoming a key component in neuroscience research, facilitating extraction of relevant information from neuronal recordings in a reasonable time. The purpose of this review is to introduce the reader to the current state-of-the-art of open-source packages for (semi)automated processing and analysis of multichannel extracellular neuronal signals (i.e., neuronal spikes, local field potentials, electroencephalogram, etc.), and the existing Neuroinformatics infrastructure for tool and data sharing. The review is concluded by pinpointing some major challenges that are being faced, which include the development of novel benchmarking techniques, cloud-based distributed processing and analysis tools, as well as defining novel means to share and standardize data. PMID:27313507

  12. Effects of a multichannel dynamic functional electrical stimulation system on hemiplegic gait and muscle forces.

    PubMed

    Qian, Jing-Guang; Rong, Ke; Qian, Zhenyun; Wen, Chen; Zhang, Songning

    2015-11-01

    [Purpose] The purpose of the study was to design and implement a multichannel dynamic functional electrical stimulation system and investigate acute effects of functional electrical stimulation of the tibialis anterior and rectus femoris on ankle and knee sagittal-plane kinematics and related muscle forces of hemiplegic gait. [Subjects and Methods] A multichannel dynamic electrical stimulation system was developed with 8-channel low frequency current generators. Eight male hemiplegic patients were trained for 4 weeks with electric stimulation of the tibia anterior and rectus femoris muscles during walking, which was coupled with active contraction. Kinematic data were collected, and muscle forces of the tibialis anterior and rectus femoris of the affected limbs were analyzed using a musculoskelatal modeling approach before and after training. A paired sample t-test was used to detect the differences between before and after training. [Results] The step length of the affected limb significantly increased after the stimulation was applied. The maximum dorsiflexion angle and maximum knee flexion angle of the affected limb were both increased significantly during stimulation. The maximum muscle forces of both the tibia anterior and rectus femoris increased significantly during stimulation compared with before functional electrical stimulation was applied. [Conclusion] This study established a functional electrical stimulation strategy based on hemiplegic gait analysis and musculoskeletal modeling. The multichannel functional electrical stimulation system successfully corrected foot drop and altered circumduction hemiplegic gait pattern.

  13. Concept of a multichannel spin-resolving electron analyzer based on Mott scattering

    PubMed Central

    Strocov, Vladimir N.; Petrov, Vladimir N.; Dil, J. Hugo

    2015-01-01

    The concept of a multichannel electron spin detector based on optical imaging principles and Mott scattering (iMott) is presented. A multichannel electron image produced by a standard angle-resolving (photo) electron analyzer or microscope is re-imaged by an electrostatic lens at an accelerating voltage of 40 kV onto the Au target. Quasi-elastic electrons bearing spin asymmetry of the Mott scattering are imaged by magnetic lenses onto position-sensitive electron CCDs whose differential signals yield the multichannel spin asymmetry image. Fundamental advantages of this concept include acceptance of inherently divergent electron sources from the electron analyzer or microscope focal plane as well as small aberrations achieved by virtue of high accelerating voltages, as demonstrated by extensive ray-tracing analysis. The efficiency gain compared with the single-channel Mott detector can be a factor of more than 104 which opens new prospects of spin-resolved spectroscopies in application not only to standard bulk and surface systems (Rashba effect, topological insulators, etc.) but also to buried heterostructures. The simultaneous spin detection combined with fast CCD readout enables efficient use of the iMott detectors at X-ray free-electron laser facilities. PMID:25931087

  14. Calibrating spectral estimation for the LISA Technology Package with multichannel synthetic noise generation

    SciTech Connect

    Ferraioli, Luigi; Hueller, Mauro; Vitale, Stefano; Heinzel, Gerhard; Hewitson, Martin; Monsky, Anneke; Nofrarias, Miquel

    2010-08-15

    The scientific objectives of the LISA Technology Package experiment on board of the LISA Pathfinder mission demand accurate calibration and validation of the data analysis tools in advance of the mission launch. The level of confidence required in the mission outcomes can be reached only by intensively testing the tools on synthetically generated data. A flexible procedure allowing the generation of a cross-correlated stationary noise time series was set up. A multichannel time series with the desired cross-correlation behavior can be generated once a model for a multichannel cross-spectral matrix is provided. The core of the procedure comprises a noise coloring, multichannel filter designed via a frequency-by-frequency eigendecomposition of the model cross-spectral matrix and a subsequent fit in the Z domain. The common problem of initial transients in a filtered time series is solved with a proper initialization of the filter recursion equations. The noise generator performance was tested in a two-dimensional case study of the closed-loop LISA Technology Package dynamics along the two principal degrees of freedom.

  15. Arctic and Antarctic Sea Ice Concentrations from Multichannel Passive-Microwave Satellite Data Sets: User's Guide

    NASA Technical Reports Server (NTRS)

    Cavalieri, Donald J.; Parkinson, Claire L.; Gloersen, Per; Zwally, H. Jay

    1997-01-01

    Satellite multichannel passive-microwave sensors have provided global radiance measurements with which to map, monitor, and study the Arctic and Antarctic polar sea ice covers. The data span over 18 years (as of April 1997), starting with the launch of the Scanning Multichannel Microwave Radiometer (SMMR) on NASA's SeaSat A and Nimbus 7 in 1978 and continuing with the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave/Imager (SSMI) series beginning in 1987. It is anticipated that the DMSP SSMI series will continue into the 21st century. The SSMI series will be augmented by new, improved sensors to be flown on Japanese and U.S. space platforms. This User's Guide provides a description of a new sea ice concentration data set generated from observations made by three of these multichannel sensors. The data set includes gridded daily ice concentrations (every-other-day for the SMMR data) for both the north and south polar regions from October 26, 1978 through September 30, 1995, with the one exception of a 6-week data gap from December 3, 1987 through January 12, 1988. The data have been placed on two CD-ROMs that include a ReadMeCD file giving the technical details on the file format, file headers, north and south polar grids, ancillary data sets, and directory structure of the CD-ROM. The CD-ROMS will be distributed by the National Snow and Ice Data Center in Boulder, CO.

  16. Design and application of multi-channel simultaneous detection system for well-earth potential

    NASA Astrophysics Data System (ADS)

    Lei, Shao; Jun, Lin; Wei, Jianrong; Sui, Yangyi; Wu, Ziyu

    2007-07-01

    Well-earth ERT (electrical resistance tomography) technology is an important geophysical exploration method which studies the location distribution of remaining oil. Based on virtual instrument technology, the author designs a set of multi-channel simultaneous detection system. It adopts multi-channel simultaneous sampling, bipolar and differential inputs, analog LPF (low pass filter), FIR digital filter, and linear accumulated digital averaging method or techniques to suppress electromagnetic noise and improve SNR (signal-to-noise ratio); uses digital signal process method to remove the overshoot, avoided huge errors and improved accuracy of measurement; adopts feedback compensative method to exclude the influence of SP(spontaneous potential) and cover a wide dynamic measurable scope; spectrum analysis method is used for judging all electrodes earthing situation correctly; the USB2.0 technique is used to solve the problem of bulky multi-channel data transmission to achieve high-speed data transmission between hardware and PC. The Liao He oilfield survey results show that the system is characterized with high efficiency, portable and strong antijiamming capability.

  17. Load-Adaptive Practical Multi-Channel Communications in Wireless Sensor Networks

    PubMed Central

    Islam, Md. Shariful; Alam, Muhammad Mahbub; Hong, Choong Seon; Lee, Sungwon

    2010-01-01

    In recent years, a significant number of sensor node prototypes have been designed that provide communications in multiple channels. This multi-channel feature can be effectively exploited to increase the overall capacity and performance of wireless sensor networks (WSNs). In this paper, we present a multi-channel communications system for WSNs that is referred to as load-adaptive practical multi-channel communications (LPMC). LPMC estimates the active load of a channel at the sink since it has a more comprehensive view of the network behavior, and dynamically adds or removes channels based on the estimated load. LPMC updates the routing path to balance the loads of the channels. The nodes in a path use the same channel; therefore, they do not need to switch channels to receive or forward packets. LPMC has been evaluated through extensive simulations, and the results demonstrate that it can effectively increase the delivery ratio, network throughput, and channel utilization, and that it can decrease the end-to-end delay and energy consumption. PMID:22163685

  18. Content-Based Multi-Channel Network Coding Algorithm in the Millimeter-Wave Sensor Network.

    PubMed

    Lin, Kai; Wang, Di; Hu, Long

    2016-07-01

    With the development of wireless technology, the widespread use of 5G is already an irreversible trend, and millimeter-wave sensor networks are becoming more and more common. However, due to the high degree of complexity and bandwidth bottlenecks, the millimeter-wave sensor network still faces numerous problems. In this paper, we propose a novel content-based multi-channel network coding algorithm, which uses the functions of data fusion, multi-channel and network coding to improve the data transmission; the algorithm is referred to as content-based multi-channel network coding (CMNC). The CMNC algorithm provides a fusion-driven model based on the Dempster-Shafer (D-S) evidence theory to classify the sensor nodes into different classes according to the data content. By using the result of the classification, the CMNC algorithm also provides the channel assignment strategy and uses network coding to further improve the quality of data transmission in the millimeter-wave sensor network. Extensive simulations are carried out and compared to other methods. Our simulation results show that the proposed CMNC algorithm can effectively improve the quality of data transmission and has better performance than the compared methods.

  19. Quantitative comparison of cortical surface reconstructions from MP2RAGE and multi-echo MPRAGE data at 3 and 7 T.

    PubMed

    Fujimoto, Kyoko; Polimeni, Jonathan R; van der Kouwe, André J W; Reuter, Martin; Kober, Tobias; Benner, Thomas; Fischl, Bruce; Wald, Lawrence L

    2014-04-15

    The Magnetization-Prepared 2 Rapid Acquisition Gradient Echo (MP2RAGE) method achieves spatially uniform contrast across the entire brain between gray matter and surrounding white matter tissue and cerebrospinal fluid by rapidly acquiring data at two points during an inversion recovery, and then combining the two volumes so as to cancel out sources of intensity and contrast bias, making it useful for neuroimaging studies at ultrahigh field strengths (≥7T). To quantify the effectiveness of the MP2RAGE method for quantitative morphometric neuroimaging, we performed tissue segmentation and cerebral cortical surface reconstruction of the MP2RAGE data and compared the results with those generated from conventional multi-echo MPRAGE (MEMPRAGE) data across a group of healthy subjects. To do so, we developed a preprocessing scheme for the MP2RAGE image data to allow for automatic cortical segmentation and surface reconstruction using FreeSurfer and analysis methods to compare the positioning of the surface meshes. Using image volumes with 1mm isotropic voxels we found a scan-rescan reproducibility of cortical thickness estimates to be 0.15 mm (or 6%) for the MEMPRAGE data and a slightly lower reproducibility of 0.19 mm (or 8%) for the MP2RAGE data. We also found that the thickness estimates were systematically smaller in the MP2RAGE data, and that both the interior and exterior cortical boundaries estimated from the MP2RAGE data were consistently positioned within the corresponding boundaries estimated from the MEMPRAGE data. Therefore several measureable differences exist in the appearance of cortical gray matter and its effect on automatic segmentation methods that must be considered when choosing an acquisition or segmentation method for studies requiring cortical surface reconstructions. We propose potential extensions to the MP2RAGE method that may help to reduce or eliminate these discrepancies.

  20. The interaction between apparent diffusion coefficients and transverse relaxation rates of human brain metabolites and water studied by diffusion-weighted spectroscopy at 7 T.

    PubMed

    Branzoli, Francesca; Ercan, Ece; Webb, Andrew; Ronen, Itamar

    2014-05-01

    The dependence of apparent diffusion coefficients (ADCs) of molecules in biological tissues on an acquisition-specific timescale is a powerful mechanism for studying tissue microstructure. Unlike water, metabolites are confined mainly to intracellular compartments, thus providing higher specificity to tissue microstructure. Compartment-specific structural and chemical properties may also affect molecule transverse relaxation times (T₂). Here, we investigated the correlation between diffusion and relaxation for N-acetylaspartate, creatine and choline compounds in human brain white matter in vivo at 7 T, and compared them with those of water under the same experimental conditions. Data were acquired in a volume of interest in parietal white matter at two different diffusion times, Δ = 44 and 246 ms, using a matrix of three echo times (T(E)) and five diffusion weighting values (up to 4575 s/mm²). Significant differences in the dependence of the ADCs on T(E) were found between water and metabolites, as well as among the different metabolites. A significant decrease in water ADC as a function of TE was observed only at the longest diffusion time (p < 0.001), supporting the hypothesis that at least part of the restricted water pool can be associated with longer T₂, as suggested by previous studies in vitro. Metabolite data showed an increase of creatine (p < 0.05) and N-acetylaspartate (p < 0.05) ADCs with TE at Δ = 44 ms, and a decrease of creatine (p < 0.05) and N-acetylaspartate (p = 0.1) ADCs with TE at Δ = 246 ms. No dependence of choline ADC on TE was observed. The metabolite results suggest that diffusion and relaxation properties are dictated not only by metabolite distribution in different cell types, but also by other mechanisms, such as interactions with membranes, exchange between "free" and "bound" states or interactions with microsusceptibility gradients.

  1. Towards high-quality simultaneous EEG-fMRI at 7 T: Detection and reduction of EEG artifacts due to head motion.

    PubMed

    Jorge, João; Grouiller, Frédéric; Gruetter, Rolf; van der Zwaag, Wietske; Figueiredo, Patrícia

    2015-10-15

    The enhanced functional sensitivity offered by ultra-high field imaging may significantly benefit simultaneous EEG-fMRI studies, but the concurrent increases in artifact contamination can strongly compromise EEG data quality. In the present study, we focus on EEG artifacts created by head motion in the static B0 field. A novel approach for motion artifact detection is proposed, based on a simple modification of a commercial EEG cap, in which four electrodes are non-permanently adapted to record only magnetic induction effects. Simultaneous EEG-fMRI data were acquired with this setup, at 7 T, from healthy volunteers undergoing a reversing-checkerboard visual stimulation paradigm. Data analysis assisted by the motion sensors revealed that, after gradient artifact correction, EEG signal variance was largely dominated by pulse artifacts (81-93%), but contributions from spontaneous motion (4-13%) were still comparable to or even larger than those of actual neuronal activity (3-9%). Multiple approaches were tested to determine the most effective procedure for denoising EEG data incorporating motion sensor information. Optimal results were obtained by applying an initial pulse artifact correction step (AAS-based), followed by motion artifact correction (based on the motion sensors) and ICA denoising. On average, motion artifact correction (after AAS) yielded a 61% reduction in signal power and a 62% increase in VEP trial-by-trial consistency. Combined with ICA, these improvements rose to a 74% power reduction and an 86% increase in trial consistency. Overall, the improvements achieved were well appreciable at single-subject and single-trial levels, and set an encouraging quality mark for simultaneous EEG-fMRI at ultra-high field.

  2. tDCS-induced alterations in GABA concentration within primary motor cortex predict motor learning and motor memory: a 7 T magnetic resonance spectroscopy study.

    PubMed

    Kim, Soyoung; Stephenson, Mary C; Morris, Peter G; Jackson, Stephen R

    2014-10-01

    Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that alters cortical excitability in a polarity specific manner and has been shown to influence learning and memory. tDCS may have both on-line and after-effects on learning and memory, and the latter are thought to be based upon tDCS-induced alterations in neurochemistry and synaptic function. We used ultra-high-field (7 T) magnetic resonance spectroscopy (MRS), together with a robotic force adaptation and de-adaptation task, to investigate whether tDCS-induced alterations in GABA and Glutamate within motor cortex predict motor learning and memory. Note that adaptation to a robot-induced force field has long been considered to be a form of model-based learning that is closely associated with the computation and 'supervised' learning of internal 'forward' models within the cerebellum. Importantly, previous studies have shown that on-line tDCS to the cerebellum, but not to motor cortex, enhances model-based motor learning. Here we demonstrate that anodal tDCS delivered to the hand area of the left primary motor cortex induces a significant reduction in GABA concentration. This effect was specific to GABA, localised to the left motor cortex, and was polarity specific insofar as it was not observed following either cathodal or sham stimulation. Importantly, we show that the magnitude of tDCS-induced alterations in GABA concentration within motor cortex predicts individual differences in both motor learning and motor memory on the robotic force adaptation and de-adaptation task.

  3. Simultaneous Multi-slice Turbo-FLASH Imaging with CAIPIRINHA for Whole Brain Distortion-Free Pseudo-Continuous Arterial Spin Labeling at 3 and 7T

    PubMed Central

    Wang, Yi; Moeller, Steen; Li, Xiufeng; Vu, An T.; Krasileva, Kate; Ugurbil, Kamil; Yacoub, Essa; Wang, Danny JJ

    2015-01-01

    Simultaneous multi-slice (SMS) or multiband (MB) imaging has recently been attempted for arterial spin labeled (ASL) perfusion MRI in conjunction with echo-planar imaging (EPI) readout. It was found that SMS-EPI can reduce the T1 relaxation effect of the label, improve image coverage and resolution with little penalty in signal-to-noise ratio (SNR). However, EPI still suffers from geometric distortion and signal dropout from field inhomogeneity effects especially at high and ultrahigh magnetic fields. Here we present a novel scheme for achieving high fidelity distortion-free quantitative perfusion imaging by combining pseudo-continuous ASL (pCASL) with SMS Turbo-FLASH (TFL) readout at both 3 and 7 Tesla. Bloch equation simulation was performed to characterize and optimize the TFL-based pCASL perfusion signal. Two MB factors (3 and 5) were implemented in SMS-TFL pCASL and compared with standard 2D TFL and EPI pCASL sequences. The temporal SNR of SMS-TFL pCASL relative to that of standard TFL pCASL was 0.76±0.10 and 0.74±0.11 at 7T, 0.70±0.05 and 0.65±0.05 at 3T for MB factor of 3 and 5, respectively. By implementing background suppression in conjunction with SMS-TFL at 3T, the relative temporal SNR improved to 0.84±0.09 and 0.79±0.10 for MB factor of 3 and 5 respectively. Compared to EPI pCASL, significantly increased temporal SNR (p<0.001) and improved visualization of orbitofrontal cortex were achieved using SMS-TFL pCASL. By combining SMS acceleration with TFL pCASL, we demonstrated the feasibility for whole brain distortion-free quantitative mapping of cerebral blood flow at high and ultrahigh magnetic fields. PMID:25837601

  4. Multi-channel spatialization systems for audio signals

    NASA Technical Reports Server (NTRS)

    Begault, Durand R. (Inventor)

    1993-01-01

    Synthetic head related transfer functions (HRTF's) for imposing reprogrammable spatial cues to a plurality of audio input signals included, for example, in multiple narrow-band audio communications signals received simultaneously are generated and stored in interchangeable programmable read only memories (PROM's) which store both head related transfer function impulse response data and source positional information for a plurality of desired virtual source locations. The analog inputs of the audio signals are filtered and converted to digital signals from which synthetic head related transfer functions are generated in the form of linear phase finite impulse response filters. The outputs of the impulse response filters are subsequently reconverted to analog signals, filtered, mixed, and fed to a pair of headphones.

  5. Multi-channel spatialization system for audio signals

    NASA Technical Reports Server (NTRS)

    Begault, Durand R. (Inventor)

    1995-01-01

    Synthetic head related transfer functions (HRTF's) for imposing reprogramable spatial cues to a plurality of audio input signals included, for example, in multiple narrow-band audio communications signals received simultaneously are generated and stored in interchangeable programmable read only memories (PROM's) which store both head related transfer function impulse response data and source positional information for a plurality of desired virtual source locations. The analog inputs of the audio signals are filtered and converted to digital signals from which synthetic head related transfer functions are generated in the form of linear phase finite impulse response filters. The outputs of the impulse response filters are subsequently reconverted to analog signals, filtered, mixed and fed to a pair of headphones.

  6. Gas phase chemical detection with an integrated chemical analysis system

    SciTech Connect

    CASALNUOVO,STEPHEN A.; FRYE-MASON,GREGORY CHARLES; KOTTENSTETTE,RICHARD; HELLER,EDWIN J.; MATZKE,CAROLYN M.; LEWIS,PATRICK R.; MANGINELL,RONALD P.; BACA,ALBERT G.; HIETALA,VINCENT M.

    2000-04-12

    Microfabrication technology has been applied to the development of a miniature, multi-channel gas phase chemical laboratory that provides fast response, small size, and enhanced versatility and chemical discrimination. Each analysis channel includes a sample preconcentrator followed by a gas chromatographic separator and a chemically selective surface acoustic wave detector array to achieve high sensitivity and selectivity. The performance of the components, individually and collectively, is described.

  7. Spatially Localized Two-Dimensional J-Resolved NMR Spectroscopy via Intermolecular Double-Quantum Coherences for Biological Samples at 7 T

    PubMed Central

    Tan, Chunhua; Cai, Shuhui; Huang, Yuqing

    2015-01-01

    Background and Purpose Magnetic resonance spectroscopy (MRS) constitutes a mainstream technique for characterizing biological samples. Benefiting from the separation of chemical shifts and J couplings, spatially localized two-dimensional (2D) J-resolved spectroscopy (JPRESS) shows better identification of complex metabolite resonances than one-dimensional MRS does and facilitates the extraction of J coupling information. However, due to variations of macroscopic magnetic susceptibility in biological samples, conventional JPRESS spectra generally suffer from the influence of field inhomogeneity. In this paper, we investigated the implementation of the localized 2D J-resolved spectroscopy based on intermolecular double-quantum coherences (iDQCs) on a 7 T MRI scanner. Materials and Methods A γ-aminobutyric acid (GABA) aqueous solution, an intact pig brain tissue, and a whole fish (Harpadon nehereus) were explored by using the localized iDQC J-resolved spectroscopy (iDQCJRES) method, and the results were compared to those obtained by using the conventional 2D JPRESS method. Results Inhomogeneous line broadening, caused by the variations of macroscopic magnetic susceptibility in the detected biological samples (the intact pig brain tissue and the whole fish), degrades the quality of 2D JPRESS spectra, particularly when a large voxel is selected and some strongly structured components are included (such as the fish spinal cord). By contrast, high-resolution 2D J-resolved information satisfactory for metabolite analyses can be obtained from localized 2D iDQCJRES spectra without voxel size limitation and field shimming. From the contrastive experiments, it is obvious that the spectral information observed in the localized iDQCJRES spectra acquired from large voxels without field shimming procedure (i.e. in inhomogeneous fields) is similar to that provided by the JPRESS spectra acquired from small voxels after field shimming procedure (i.e. in relatively homogeneous fields

  8. Mapping of brain macromolecules and their use for spectral processing of (1)H-MRSI data with an ultra-short acquisition delay at 7 T.

    PubMed

    Považan, Michal; Hangel, Gilbert; Strasser, Bernhard; Gruber, Stephan; Chmelik, Marek; Trattnig, Siegfried; Bogner, Wolfgang

    2015-11-01

    Long echo time (TE) MR spectroscopy (MRS) sequences are sensitive only to metabolites of low molecular weight. At shorter TE, significantly more metabolite signals are detectable, including broad signals of high-molecular-weight macromolecules (MMs). Although the presence of MM resonances can bias metabolite quantification at short TE, proper quantification of MMs is important since MMs themselves may serve as potentially valuable biomarkers for many pathologies. We have therefore developed an FID-based 2D-MR Spectroscopic Imaging (2D-MRSI) sequence to map MMs in healthy brain tissue at 7 T within a scan time of ~17 min and a repetition time of 879 ms. This 2D-MRSI technique provides MM maps over a whole slice (i.e., including cortical gray matter) at an ultra-short acquisition delay of 1.3 ms, using double inversion for efficient nulling of low-molecular-weight metabolites. The optimal sequence parameters were estimated using Bloch simulations, phantom testing, and in vivo validation. The acquired in vivo MM spectra (n=6) included nine distinct MM peaks in the range of ~0.9-3.7 ppm. The measured average MM spectrum was incorporated into the LCModel basis set and utilized for further quantification of MRSI data sets without metabolite nulling, which were acquired in five additional volunteers. The quantification results for two basis sets, one including the MMs and one without MM spectrum, were compared. Due to the high spectral resolution and full signal detection provided by the FID-MRSI sequence, we could successfully map five important brain metabolites. Most quantified metabolite signal amplitudes were significantly lower since the inclusion of MMs into the basis set corrected the overestimation of metabolite signals. The precision of fit (i.e., Cramér Rao lower bounds) remained unchanged. Our MM maps show that the overall MM contribution was higher in gray matter than in white matter. In conclusion, the acquired MM spectrum improved the accuracy of

  9. Depth-resolved surface coil MRS (DRESS)-localized dynamic (31) P-MRS of the exercising human gastrocnemius muscle at 7 T.

    PubMed

    Valkovič, Ladislav; Chmelík, Marek; Just Kukurová, Ivica; Jakubová, Michaela; Kipfelsberger, Monika Christina; Krumpolec, Patrik; Tušek Jelenc, Marjeta; Bogner, Wolfgang; Meyerspeer, Martin; Ukropec, Jozef; Frollo, Ivan; Ukropcová, Barbara; Trattnig, Siegfried; Krššák, Martin

    2014-11-01

    Dynamic (31) P-MRS with sufficiently high temporal resolution enables the non-invasive evaluation of oxidative muscle metabolism through the measurement of phosphocreatine (PCr) recovery after exercise. Recently, single-voxel localized (31) P-MRS was compared with surface coil localization in a dynamic fashion, and was shown to provide higher anatomical and physiological specificity. However, the relatively long TE needed for the single-voxel localization scheme with adiabatic pulses limits the quantification of J-coupled spin systems [e.g. adenosine triphosphate (ATP)]. Therefore, the aim of this study was to evaluate depth-resolved surface coil MRS (DRESS) as an alternative localization method capable of free induction decay (FID) acquisition for dynamic (31) P-MRS at 7 T. The localization performance of the DRESS sequence was tested in a phantom. Subsequently, two dynamic examinations of plantar flexions at 25% of maximum voluntary contraction were conducted in 10 volunteers, one examination with and one without spatial localization. The DRESS slab was positioned obliquely over the gastrocnemius medialis muscle, avoiding other calf muscles. Under the same load, significant differences in PCr signal drop (31.2 ± 16.0% versus 43.3 ± 23.4%), end exercise pH (7.06 ± 0.02 versus 6.96 ± 0.11), initial recovery rate (0.24 ± 0.13 mm/s versus 0.35 ± 0.18 mm/s) and maximum oxidative flux (0.41 ± 0.14 mm/s versus 0.54 ± 0.16 mm/s) were found between the non-localized and DRESS-localized data, respectively. Splitting of the inorganic phosphate (Pi) signal was observed in several non-localized datasets, but in none of the DRESS-localized datasets. Our results suggest that the application of the DRESS localization scheme yielded good spatial selection, and provided muscle-specific insight into oxidative metabolism, even at a relatively low exercise load. In addition, the non-echo-based FID acquisition allowed for reliable detection of ATP resonances, and therefore

  10. Design Study of a Multi-channel Array Particle Spectrometer for Space Missions

    NASA Astrophysics Data System (ADS)

    Trindade, Andreia; Assis, P.; Brogueira, P.; Gonçalves, P.; Keating, A.; Pimenta, M.; Rodrigues, P.; Trindade, A.

    In this work, a novel particle spectrometer is proposed to fulfil the need to map the space radiation environment for future space missions and to provide more accurate scientific data. The concept of the instrument brings together new radiation-hard technologies, for the photo-sensors and scintillating materials that will improve the quality of the data, while taking into account the limited resources such as mass, power and accommodation, allocated for space radiation monitors. The Multi-channel Array Particle Spectrometer (MAPS), can measure fluxes and energy dis-tributions of protons, ions, electrons and gammas in a wide energy range based on the 3D reconstruction of the particle track through the detector and its deposited energy in the active volume. It consists on a 8 x 8 segmented scintillator block built from 3.2 x 3.2 x 20 mm3 indi-vidual LYSO:Ce rods that are readout at both ends by two 64 pixel Silicon Photo-Multipliers (SiPMs) matrices, a new generation of high gain (105-106) avalanche photodiodes working in controlled Geiger mode, that collect the scintillating light produced by the interactions of the charged particles in the crystals. Each SiPM matrix is readout by a 64 channel mixed sig-nal analog-digital ASIC, offering both particle identification and particle counting capabilities. Power cycling design of the ASIC allows to activate the particle identification block only during a pre-determined time slice, keeping the total power budget of less than 1 mW/channel. An on-board FPGA sorts the serialized data from the two ASICs and computes the trigger primitives in real-time and in an event-by-event basis. Whenever a charged particle crosses the segmented volume of the detector, the XY coordinates, given by the pixelized crystal positions, and the deposited energy in each crystal is recorded. The double readout scheme allows to compute the light collection asymmetry between both ends of the crystal and to use that information to record the

  11. Effect of magnetic yoke on magnetic field distribution and intercepting effect of multi-channel cascading magnet arrays

    NASA Astrophysics Data System (ADS)

    Zhang, S. P.; Wu, P.; Wang, L.; Li, F. C.; Chen, S.; Sun, S. F.

    2010-03-01

    `Magnetic-Sieve' possesses a potential use in oxygen separation. The effect of a magnetic yoke on magnetic field distribution and intercepting effect of multi-channel cascading magnet arrays in a `Magnetic-Sieve' configuration is studied by ANSYS finite element software. The multi-channel cascading magnet arrays consist of cuboid neodymium-iron-boron permanent magnets. The size of the magnets is W×H = 38 mm×5 mm, and the clearance between two adjacent magnets is 1 mm. The results show that the intercepting effect tends to decrease from the central channel to the most lateral channels in multi-channel cascading magnet arrays. Compared with the simulation result of two magnets, the central magnetic inductions of the center channel and the most lateral channels in the multi-channel cascading magnet array including 14 magnets decrease respectively 10% and 31%, and the intercepting effects of the center channel and the most lateral channels decrease 19% and 60%, respectively. When the magnetic yoke is added on the multi-channel cascading magnet array, the above-mentioned four values are increased by 28%, 29%, 63% and 65%, respectively. The simulation study shows that the introducing of magnetic yokes can enhance the central magnetic induction and the intercepting effect of the gradient magnetic field, and moreover, reduce the disparities of intercepting effect among the channels.

  12. Multichannel seismic/weather/Zoological monitoring of the oceans

    NASA Astrophysics Data System (ADS)

    Hello, Yann; Bonnieux, Sebastien; Sukovitch, Alexey; Argentino, Jean-Francois; Nolet, Guust

    2013-04-01

    position. A second, dual channel, prototype version of Mermaid using two dedicated hydrophones is designed to enlarge the band pass for acoustic signals with much higher frequency than seismic. Based on the same algorithm using wavelet transforms, Mermaid continuously analyzes acoustic signals to detect both major seismic events and weather phenomena such rain, drizzle, open sea and ice, or whale migration, during its drift phase. This extension to multi-purpose applications makes the Mermaid very attractive for the Argo program. In fact, Mermaids using passive low cost sensors form a very light and complementary solution that can be integrated with an Argo float; Mermaids listen during the passive drift while CTD data are taken during ascent and descent. Such multidisciplinary approach should allow seismologists to participate in international program such as Argo and obtain the dense ocean coverage needed to image the deep structure of the Earth.

  13. Reentrant topological phase transitions in a disordered spinless superconducting wire

    NASA Astrophysics Data System (ADS)

    Rieder, Maria-Theresa; Brouwer, Piet W.; Adagideli, İnanç

    2013-08-01

    In a one-dimensional spinless p-wave superconductor with coherence length ξ, disorder induces a phase transition between a topologically nontrivial phase and a trivial insulating phase at the critical mean-free path l=ξ/2. Here, we show that a multichannel spinless p-wave superconductor goes through an alternation of topologically trivial and nontrivial phases upon increasing the disorder strength, the number of phase transitions being equal to the channel number N. The last phase transition, from a nontrivial phase into the trivial phase, takes place at a mean-free path l=ξ/(N+1), parametrically smaller than the critical mean-free path in one dimension. Our result is valid in the limit that the wire width W is much smaller than the superconducting coherence length ξ.

  14. 3D multi-channel bi-functionalized silk electrospun conduits for peripheral nerve regeneration.

    PubMed

    Dinis, T M; Elia, R; Vidal, G; Dermigny, Q; Denoeud, C; Kaplan, D L; Egles, C; Marin, F

    2015-01-01

    Despite technological advances over the past 25 years, a complete recovery from peripheral nerve injuries remains unsatisfactory today. The autograft is still considered the "gold standard" in clinical practice; however, postoperative complications and limited availability of nerve tissue have motivated the development of alternative approaches. Among them, the development of biomimetic nerve graft substitutes is one of the most promising strategies. In this study, multichanneled silk electrospun conduits bi-functionalized with Nerve Growth Factor (NGF) and Ciliary Neurotropic Factor (CNTF) were fabricated to enhance peripheral nerve regeneration. These bioactive guides consisting of longitudinally oriented channels and aligned nanofibers were designed in order to mimic the fascicular architecture and fibrous extracellular matrix found in native nerve. The simple use of the electrospinning technique followed by a manual manipulation to manufacture these conduits provides tailoring of channel number and diameter size to create perineurium-like structures. Functionalization of the silk fibroin nanofiber did not affect its secondary structure and chemical property. ELISA assays showed the absence of growth factors passive release from the functionalized fibers avoiding the topical accumulation of proteins. In addition, our biomimetic multichanneled functionalized nerve guides displayed a mechanical behavior comparable to that of rat sciatic nerve with an ultimate peak stress of 4.0 ± 0.6 MPa and a corresponding elongation at failure of 156.8 ± 46.7%. Taken together, our results demonstrate for the first time our ability to design and characterize a bi-functionalized nerve conduit consisting of electrospun nanofibers with multichannel oriented and nanofibers aligned for peripheral regeneration. Our bioactive silk tubes thus represent a new and promising technique towards the creation of a biocompatible nerve guidance conduit. PMID:25460402

  15. Improvement of force-sensor-based heart rate estimation using multichannel data fusion.

    PubMed

    Bruser, Christoph; Kortelainen, Juha M; Winter, Stefan; Tenhunen, Mirja; Parkka, Juha; Leonhardt, Steffen

    2015-01-01

    The aim of this paper is to present and evaluate algorithms for heartbeat interval estimation from multiple spatially distributed force sensors integrated into a bed. Moreover, the benefit of using multichannel systems as opposed to a single sensor is investigated. While it might seem intuitive that multiple channels are superior to a single channel, the main challenge lies in finding suitable methods to actually leverage this potential. To this end, two algorithms for heart rate estimation from multichannel vibration signals are presented and compared against a single-channel sensing solution. The first method operates by analyzing the cepstrum computed from the average spectra of the individual channels, while the second method applies Bayesian fusion to three interval estimators, such as the autocorrelation, which are applied to each channel. This evaluation is based on 28 night-long sleep lab recordings during which an eight-channel polyvinylidene fluoride-based sensor array was used to acquire cardiac vibration signals. The recruited patients suffered from different sleep disorders of varying severity. From the sensor array data, a virtual single-channel signal was also derived for comparison by averaging the channels. The single-channel results achieved a beat-to-beat interval error of 2.2% with a coverage (i.e., percentage of the recording which could be analyzed) of 68.7%. In comparison, the best multichannel results attained a mean error and coverage of 1.0% and 81.0%, respectively. These results present statistically significant improvements of both metrics over the single-channel results (p < 0.05).

  16. Comparison of planform multi-channel network characteristics of alluvial and bedrock constrained large rivers

    NASA Astrophysics Data System (ADS)

    Carling, P. A.; Meshkova, L.; Robinson, R. A.

    2011-12-01

    The Mekong River in northern Cambodia is an multi-channel mixed bedrock-alluvial river but it was poorly researched until present. Preliminary study of the Mekong geomorphology was conducted by gathering existing knowledge of its geological and tectonic settings, specific riparian vegetation and ancient alluvial terraces in which the river has incised since the Holocene. Altogether this process has allowed a geomorphological portrait of the river to be composed within the Quaternary context. Following this outline, the planform characteristics of the Mekong River network are compared, using analysis of channel network and islands configurations, with the fluvial patterns of the Orange River (South Africa), Upper Columbia River (Canada) and the Ganga River (India, Bangladesh). These rivers are selected as examples of multi-channel mixed bedrock alluvial, anastomosed alluvial and braided alluvial rivers respectively. Network parameters such as channel bifurcation angles asymmetry, sinuosity, braid intensity and island morphometric shape metrics are compared and contrasted between bedrock and alluvial systems. In addition, regional and local topographic trend surfaces produced for each river planform help explain the local changes in river direction and the degree of anastomosis, and distinguish the bedrock-alluvial rivers from the alluvial rivers. Variations between planform characteristics are to be explained by channel forming processes and in the case of mixed bedrock-alluvial rivers mediated by structural control. Channel metrics (derived at the reach-scale) provide some discrimination between different multi-channel patterns but are not always robust when considered singly. In contrast, island shape metrics (obtained at subreach-scale) allow robust discrimination between alluvial and bedrock systems.

  17. Spherical Deconvolution of Multichannel Diffusion MRI Data with Non-Gaussian Noise Models and Spatial Regularization.

    PubMed

    Canales-Rodríguez, Erick J; Daducci, Alessandro; Sotiropoulos, Stamatios N; Caruyer, Emmanuel; Aja-Fernández, Santiago; Radua, Joaquim; Yurramendi Mendizabal, Jesús M; Iturria-Medina, Yasser; Melie-García, Lester; Alemán-Gómez, Yasser; Thiran, Jean-Philippe; Sarró, Salvador; Pomarol-Clotet, Edith; Salvador, Raymond

    2015-01-01

    Spherical deconvolution (SD) methods are widely used to estimate the intra-voxel white-matter fiber orientations from diffusion MRI data. However, while some of these methods assume a zero-mean Gaussian distribution for the underlying noise, its real distribution is known to be non-Gaussian and to depend on many factors such as the number of coils and the methodology used to combine multichannel MRI signals. Indeed, the two prevailing methods for multichannel signal combination lead to noise patterns better described by Rician and noncentral Chi distributions. Here we develop a Robust and Unbiased Model-BAsed Spherical Deconvolution (RUMBA-SD) technique, intended to deal with realistic MRI noise, based on a Richardson-Lucy (RL) algorithm adapted to Rician and noncentral Chi likelihood models. To quantify the benefits of using proper noise models, RUMBA-SD was compared with dRL-SD, a well-established method based on the RL algorithm for Gaussian noise. Another aim of the study was to quantify the impact of including a total variation (TV) spatial regularization term in the estimation framework. To do this, we developed TV spatially-regularized versions of both RUMBA-SD and dRL-SD algorithms. The evaluation was performed by comparing various quality metrics on 132 three-dimensional synthetic phantoms involving different inter-fiber angles and volume fractions, which were contaminated with noise mimicking patterns generated by data processing in multichannel scanners. The results demonstrate that the inclusion of proper likelihood models leads to an increased ability to resolve fiber crossings with smaller inter-fiber angles and to better detect non-dominant fibers. The inclusion of TV regularization dramatically improved the resolution power of both techniques. The above findings were also verified in human brain data.

  18. Spherical Deconvolution of Multichannel Diffusion MRI Data with Non-Gaussian Noise Models and Spatial Regularization

    PubMed Central

    Canales-Rodríguez, Erick J.; Caruyer, Emmanuel; Aja-Fernández, Santiago; Radua, Joaquim; Yurramendi Mendizabal, Jesús M.; Iturria-Medina, Yasser; Melie-García, Lester; Alemán-Gómez, Yasser; Thiran, Jean-Philippe; Sarró, Salvador; Pomarol-Clotet, Edith; Salvador, Raymond

    2015-01-01

    Spherical deconvolution (SD) methods are widely used to estimate the intra-voxel white-matter fiber orientations from diffusion MRI data. However, while some of these methods assume a zero-mean Gaussian distribution for the underlying noise, its real distribution is known to be non-Gaussian and to depend on many factors such as the number of coils and the methodology used to combine multichannel MRI signals. Indeed, the two prevailing methods for multichannel signal combination lead to noise patterns better described by Rician and noncentral Chi distributions. Here we develop a Robust and Unbiased Model-BAsed Spherical Deconvolution (RUMBA-SD) technique, intended to deal with realistic MRI noise, based on a Richardson-Lucy (RL) algorithm adapted to Rician and noncentral Chi likelihood models. To quantify the benefits of using proper noise models, RUMBA-SD was compared with dRL-SD, a well-established method based on the RL algorithm for Gaussian noise. Another aim of the study was to quantify the impact of including a total variation (TV) spatial regularization term in the estimation framework. To do this, we developed TV spatially-regularized versions of both RUMBA-SD and dRL-SD algorithms. The evaluation was performed by comparing various quality metrics on 132 three-dimensional synthetic phantoms involving different inter-fiber angles and volume fractions, which were contaminated with noise mimicking patterns generated by data processing in multichannel scanners. The results demonstrate that the inclusion of proper likelihood models leads to an increased ability to resolve fiber crossings with smaller inter-fiber angles and to better detect non-dominant fibers. The inclusion of TV regularization dramatically improved the resolution power of both techniques. The above findings were also verified in human brain data. PMID:26470024

  19. High-pressure duo-multichannel soft x-ray spectrometer for tokamak plasma diagnostics

    SciTech Connect

    Schwob, J.L.; Wouters, A.W.; Suckewer, S.

    1987-03-01

    A high-resolution, time-resolving soft X-ray multichannel spectrometer (SOXMOS) that permits the simultaneous measurement of emission in two different spectral ranges has been developed and tested extensively for tokamak plasma diagnostics. The basic instrument is a high-resolution, interferometrically adjusted, extreme grazing incidence Schwob-Fraenkel duochromator. The instrument is equipped with two multichannel detectors that are adjusted interferometrically and scan along the Rowland circle. Each consists of an MgF/sub 2/ coated, funneled microchannel plate, associated with a phosphor screen image intensifier that is coupled to a 1024-element photodiode array by a flexible fibrer optic conduit. The total wavelength coverage of the instrument is 5 to 340/sup 0/ A with a measured resolution (FWHM) of about 0.2 A when equipped with a 600 g/mm grating, and 5 to 85 A with a resolution of about 0.06 A using a 2400 g/mm grating. The simultaneous spectral coverage of each detector varies from 15 A at the short wavelength limit to 70 A at the long wavelength limit with the lower dispersion grating. The minimum read-out time for a full spectral portion is 17 ms, but several individual lines can be measured with 1 ms time resolution by selected pixel readout. Higher time resolution can be achieved by replacing one multichannel detector with a single channel electron multiplier detector. Examples of data from the PLT and TFTR tokamaks are presented to illustrate the instrument's versatility, high spectral resolution, and high signal-to-noise ratio even in the 10 A region. 44 refs., 20 figs.

  20. Real-time characterization of film growth on transparent substrates by rotating-compensator multichannel ellipsometry.

    PubMed

    Lee, J; Collins, R W

    1998-07-01

    A multichannel spectroscopic ellipsometer in the fixed-polarizer-sample-rotating-compensator-fixed-analyzer (PSC(R)A) configuration has been developed and applied for real-time characterization of the nucleation and growth of thin films on transparent substrates. This rotating-compensator design overcomes the major disadvantages of the multichannel ellipsometer in the rotating-polarizer-sample-fixed-analyzer (P(R)SA) configuration while retaining its high speed and precision for the characterization of thin-film processes in real time. The advantages of the PSC(R)A configuration include (i) its high accuracy and precision for the detection of low-ellipticity polarization states that are generated upon reflection of linearly polarized light from transparent film-substrate systems, and (ii) the ability to characterize depolarization of the reflected light, an effect that leads to errors in ellipticity when measured with the P(R)SA configuration. A comparison of the index of refraction spectra for a glass substrate obtained in the real-time PSC(R)A mode in 2.5 s and in the ex situ fixed-polarizer-fixed-compensator-sample-rotating-analyzer (PCSA(R)) mode in ~10 min show excellent agreement, with a standard deviation between the two data sets of 8 x 10(-4), computed over the photon energy range from 1.5 to 3.5 eV. First, we describe the PSC(R)A ellipsometer calibration procedures developed specifically for transparent substrates. In addition, we describe the application of the multichannel PSC(R)A instrument for a study of thin-film diamond nucleation and growth on glass in a low-temperature microwave plasma-enhanced chemical vapor deposition process. PMID:18285868

  1. Spherical Deconvolution of Multichannel Diffusion MRI Data with Non-Gaussian Noise Models and Spatial Regularization.

    PubMed

    Canales-Rodríguez, Erick J; Daducci, Alessandro; Sotiropoulos, Stamatios N; Caruyer, Emmanuel; Aja-Fernández, Santiago; Radua, Joaquim; Yurramendi Mendizabal, Jesús M; Iturria-Medina, Yasser; Melie-García, Lester; Alemán-Gómez, Yasser; Thiran, Jean-Philippe; Sarró, Salvador; Pomarol-Clotet, Edith; Salvador, Raymond

    2015-01-01

    Spherical deconvolution (SD) methods are widely used to estimate the intra-voxel white-matter fiber orientations from diffusion MRI data. However, while some of these methods assume a zero-mean Gaussian distribution for the underlying noise, its real distribution is known to be non-Gaussian and to depend on many factors such as the number of coils and the methodology used to combine multichannel MRI signals. Indeed, the two prevailing methods for multichannel signal combination lead to noise patterns better described by Rician and noncentral Chi distributions. Here we develop a Robust and Unbiased Model-BAsed Spherical Deconvolution (RUMBA-SD) technique, intended to deal with realistic MRI noise, based on a Richardson-Lucy (RL) algorithm adapted to Rician and noncentral Chi likelihood models. To quantify the benefits of using proper noise models, RUMBA-SD was compared with dRL-SD, a well-established method based on the RL algorithm for Gaussian noise. Another aim of the study was to quantify the impact of including a total variation (TV) spatial regularization term in the estimation framework. To do this, we developed TV spatially-regularized versions of both RUMBA-SD and dRL-SD algorithms. The evaluation was performed by comparing various quality metrics on 132 three-dimensional synthetic phantoms involving different inter-fiber angles and volume fractions, which were contaminated with noise mimicking patterns generated by data processing in multichannel scanners. The results demonstrate that the inclusion of proper likelihood models leads to an increased ability to resolve fiber crossings with smaller inter-fiber angles and to better detect non-dominant fibers. The inclusion of TV regularization dramatically improved the resolution power of both techniques. The above findings were also verified in human brain data. PMID:26470024

  2. Wideband Multichannel Time-Reversal Processing for Acoustic Communications in a Tunnel-like Structure

    SciTech Connect

    Candy, J V; Chambers, D H; Robbins, C L; Guidry, B L; Poggio, A J; Dowla, F; Hertzog, C A

    2006-01-12

    The development of multichannel time-reversal (T/R) processing techniques continues to progress rapidly especially when the need to communicate in a highly reverberative environment becomes critical. The underlying T/R concept is based on time-reversing the Green's function characterizing the uncertain communications channel investigating the deleterious dispersion and multipath effects. In this paper, attention is focused on two major objectives: (1) wideband communications leading to a time reference modulation technique; and (2) multichannel acoustic communications in a tunnel (or cave or pipe) with many obstructions, multipath returns, severe background noise, disturbances, long propagation paths ({approx}180) with disruptions (bends). For this extremely hostile environment, it is shown that multichannel T/R receivers can easily be extended to the wideband designs while demonstrating their performance in both the ''canonical'' stairwell of our previous work as well as a tunnel-like structure. Acoustic information signals are transmitted with an 8-element host or base station array to two client receivers with a significant loss in signal levels due to the propagation environment. In this paper, the results of the new wideband T/R processor and modulation scheme are discussed to demonstrate the overall performance for both high (24-bit) and low (1-bit) bit level analog-to-digital (A/D) converter designs. These results are validated by performing proof-of-principle acoustic communications experiments in air. It is shown that the resulting T/R receivers are capable of extracting the transmitted coded sequence from noisy microphone array measurements with zero-bit error.

  3. A low-cost multichannel wireless neural stimulation system for freely roaming animals

    NASA Astrophysics Data System (ADS)

    Alam, Monzurul; Chen, Xi; Fernandez, Eduardo

    2013-12-01

    Objectives. Electrical stimulation of nerve tissue and recording of neural activity are the basis of many therapies and neural prostheses. Conventional stimulation systems have a number of practical limitations, especially in experiments involving freely roaming subjects. Our main objective was to develop a modular, versatile and inexpensive multichannel wireless system able to overcome some of these constraints. Approach. We have designed and implemented a new multichannel wireless neural stimulator based on commercial components. The system is small (2 cm × 4 cm × 0.5 cm) and light in weight (9 g) which allows it to be easily carried in a small backpack. To test and validate the performance and reliability of the whole system we conducted several bench tests and in vivo experiments. Main results. The performance and accuracy of the stimulator were comparable to commercial threaded systems. Stimulation sequences can be constructed on-the-fly with 251 selectable current levels (from 0 to 250 µA) with 1 µA step resolution. The pulse widths and intervals can be as long as 65 ms in 2 µs time resolution. The system covers approximately 10 m of transmission range in a regular laboratory environment and 100 m in free space (line of sight). Furthermore it provides great flexibility for experiments since it allows full control of the stimulator and the stimulation parameters in real time. When there is no stimulation, the device automatically goes into low-power sleep mode to preserve battery power. Significance. We introduce the design of a powerful multichannel wireless stimulator assembled from commercial components. Key features of the system are their reliability, robustness and small size. The system has a flexible design that can be modified straightforwardly to tailor it to any specific experimental need. Furthermore it can be effortlessly adapted for use with any kind of multielectrode arrays.

  4. A new approach of watermarking technique by means multichannel wavelet functions

    NASA Astrophysics Data System (ADS)

    Agreste, Santa; Puccio, Luigia

    2012-12-01

    The digital piracy involving images, music, movies, books, and so on, is a legal problem that has not found a solution. Therefore it becomes crucial to create and to develop methods and numerical algorithms in order to solve the copyright problems. In this paper we focus the attention on a new approach of watermarking technique applied to digital color images. Our aim is to describe the realized watermarking algorithm based on multichannel wavelet functions with multiplicity r = 3, called MCWM 1.0. We report a large experimentation and some important numerical results in order to show the robustness of the proposed algorithm to geometrical attacks.

  5. Calculation of rotational--vibrational preionization in H/sub 2/ by multichannel quantum defect theory

    SciTech Connect

    Jungen, C.; Dill, D.

    1980-10-01

    Multichannel quantum defect theory is adapted to treat simultaneous rotational and vibrational preionization in H/sub 2/. The strongly preionized spectrum between the N/sup +/=0 and N/sup +/=2 rotational thresholds of photoionization of H/sub 2/X/sup 1/..sigma../sub g//sup +/(J''=0, v''=0) to produce H/sub 2//sup +/X/sup 2/..sigma../sub g//sup +/(N/sup +/, v/sup +/=0) is computed as example and good agreement is obtained with the photoionization data of Dehmer and Chupka.

  6. Coherent state transfer through a multi-channel quantum network: Natural versus controlled evolution passage

    NASA Astrophysics Data System (ADS)

    Chen, Bing; Li, Yong

    2016-04-01

    Quantum state transfer (QST) is an important task in quantum information processing. In this study, we describe two approaches for the high-fidelity transfer of a quantum state between two opposite quantum dots attached to a multi-channel quantum network. First, we demonstrate that a high-efficiency QST can be achieved with the coherent time evolution of a quantum system without any external control. Second, we present an approach that uses an alternative mechanism for a high-fidelity QST. By adiabatically varying tunnel couplings, it is possible to implement the complete transmission of a quantum state based on this quantum mechanical mechanism.

  7. Multichannel broadcast based on home channel for cognitive radio sensor networks.

    PubMed

    Zeng, Fanzi; Tang, Yuting; Pu, Jianjie

    2014-01-01

    Considering the limited resources and the dynamic spectrum distribution in the cognitive radio sensor networks (CRSN), a half-duplex Multichannel broadcast protocol for CRSN is presented based on the home channel. This protocol maintains the networks topology only through the home channel, so there is no need for the public channel to transmit the control information and no need for the synchronization. After network initialization, node broadcasts data via home channel in half-duplex transmission way. The simulation results show that, compared with complete broadcast, the proposed protocol effectively reduces broadcast delay and overhead. PMID:25161397

  8. Rapid identification of bacterial biofilms and biofilm wound models using a multichannel nanosensor.

    PubMed

    Li, Xiaoning; Kong, Hao; Mout, Rubul; Saha, Krishnendu; Moyano, Daniel F; Robinson, Sandra M; Rana, Subinoy; Zhang, Xinrong; Riley, Margaret A; Rotello, Vincent M

    2014-12-23

    Identification of infectious bacteria responsible for biofilm-associated infections is challenging due to the complex and heterogeneous biofilm matrix. To address this issue and minimize the impact of heterogeneity on biofilm identification, we developed a gold nanoparticle (AuNP)-based multichannel sensor to detect and identify biofilms based on their physicochemical properties. Our results showed that the sensor can discriminate six bacterial biofilms including two composed of uropathogenic bacteria. The capability of the sensor was further demonstrated through discrimination of biofilms in a mixed bacteria/mammalian cell in vitro wound model.

  9. Multichannel optical add-drop processes in symmetrical waveguide-resonator systems.

    PubMed

    Jiang, Wei; Chen, Ray T

    2003-11-21

    Multichannel optical add-drop processes are studied in a class of symmetric waveguide-resonator systems. With insight gained from group theory, we analyze these systems and show that they can add or drop multiple wavelengths simultaneously, with 100% efficiency. A new mechanism is presented to reduce the remnant light at the dropped wavelengths in the pass-through port. High-order Butterworth filters can also be achieved in these systems. Built upon conventional or photonic-crystal based structures, these systems can be used in optical communication applications.

  10. Note: Design principles of a linear array multi-channel effusive metal-vapor atom source

    SciTech Connect

    Jana, B.; Majumder, A.; Thakur, K. B.; Das, A. K.

    2013-10-15

    Atomic beams can easily be produced by allowing atoms to effuse through a channel. In an earlier investigation [A. Majumder et al., Vacuum 83, 989 (2009)], we had designed, fabricated, and characterized an effusive metal-vapor source using collinear-array of multi-channel. In this note, we describe the theoretical basis of designing the source. Atom density in atomic beam has been estimated using a set of analytical expressions for long-channel operated in transparent mode. Parametric studies on aspect ratio of channel, inter-channel separation, beam width, and vertical distance from the source are carried out. They are useful in providing physical picture and optimizing design parameters.

  11. Reprocessing of multi-channel seismic-reflection data collected in the Chukchi Sea

    USGS Publications Warehouse

    Agena, W.F.; Lee, M.W.; Hart, P.E.

    2001-01-01

    Contained on this set of two CD-ROMs are stacked and migrated multi-channel seismic-reflection data for 44 lines recorded in the Chukchi Sea, northern Alaska, by the United States Geological Survey in 1977, 1978, and 1980. All data were reprocessed by the USGS in 2000 using updated methods. The resulting final data have both increased temporal and spatial resolution thus providing improved interpretability. An added benefit of these CD-ROMs is that they are a more stable, long-term archival medium for the data.

  12. Field test results with the targeted search MCSA. [multi-channel spectrum analyzer for SETI

    NASA Technical Reports Server (NTRS)

    Tarter, J. C.

    1988-01-01

    In April 1985, a 74,000 channel prototype of the multichannel spectrum analyzer (MCSA) that NASA plans to use in a systematic search for extraterrestrial intelligence (SETI) was installed at DSS13, a 26 meter R&D antenna facility at the Goldstone Deep Space Network (DSN) site. Since that time the instrumentation has been used to validate the performance of signal detection algorithms using locally injected signals and the weak carriers from distant spacecraft. This paper describes results from the Goldstone Field Tests and plans to move the prototype equipment to other sites where SETI may be conducted in the future.

  13. Multi-channel optical pyrometer for sub-nanosecond temperature measurements at NDCX-I/II

    SciTech Connect

    Ni, P.A.; Bieniosek, F.M.; Waldron, W.L.

    2011-04-13

    We present a detailed technical description of a fast multi-channel pyrometer designed for warm-dense-matter (WDM) experiments with intense heavy ion beams at the neutralized-drift-compression-experiment linear accelerator (NDCX-I/II) at Lawrence Berkeley National Laboratory (LBNL). The unique features of the described instrument are its sub-nanosecond temporal resolution (100 ps rise-time) and a broad range, 1,500 K - 12,000 K of measurable brightness temperatures in the visible and near-infrared regions of the spectrum. The working scheme, calibration procedure, experimental data obtained with the pyrometer and future applications are presented.

  14. Effects, determination, and correction of count rate nonlinearity in multi-channel analog electron detectors

    SciTech Connect

    Reber, T. J.; Plumb, N. C.; Waugh, J. A.; Dessau, D. S.

    2014-04-15

    Detector counting rate nonlinearity, though a known problem, is commonly ignored in the analysis of angle resolved photoemission spectroscopy where modern multichannel electron detection schemes using analog intensity scales are used. We focus on a nearly ubiquitous “inverse saturation” nonlinearity that makes the spectra falsely sharp and beautiful. These artificially enhanced spectra limit accurate quantitative analysis of the data, leading to mistaken spectral weights, Fermi energies, and peak widths. We present a method to rapidly detect and correct for this nonlinearity. This algorithm could be applicable for a wide range of nonlinear systems, beyond photoemission spectroscopy.

  15. Depositional and tectonic framework of the rift basins of Lake Baikal from multichannel seismic data

    USGS Publications Warehouse

    Hutchinson, D.R.; Golmshtok, A.J.; Zonenshain, L.P.; Moore, T.C.; Scholz, C.A.; Klitgord, Kim D.

    1992-01-01

    Recent multichannel seismic reflection data from Lake Baikal, located in a large, active, continental rift in central Asia, image three major stratigraphic units totalling 3.5 to 7.5 km thick in four subbasins. A major change in rift deposition and faulting between the oldest and middle-rift units probably corresponds to the change from slow to fast rifting. A brief comparison of the basins of Lake Baikal with those of the East African rift system highlights differences in structural style that can be explained by differences in age and evolution of the surrounding basement rocks. -from Authors

  16. A multi-channel ADC for use in the PHENIX detector

    SciTech Connect

    Emery, M.S.; Frank, S.S.; Britton, C.L. Jr.; Wintenberg, A.L.; Simpson, M.L.; Ericson, M.N.; Young, G.R.; Clonts, L.G.; Allen, M.D.

    1996-12-31

    A custom CMOS analog to digital converter was designed and a prototype 8-channel ADC ASIC was fabricated in a 1.2 {mu}m process. The circuit uses a Wilkinson-type architecture which is suitable for use in multi-channel applications such as the PHENIX detector. The ADC design features include a differential positive-ECL input for the high speed clock and selectable control for 11 or 12-bit conversions making it suitable for use in multiple PHENIX subsystems. Circuit topologies and ASIC layout specifics. including power consumption, maximum clock speed, INL. and DNL are discussed. The ADC performed to 11-bit accuracy.

  17. Multichannel broadcast based on home channel for cognitive radio sensor networks.

    PubMed

    Zeng, Fanzi; Tang, Yuting; Pu, Jianjie

    2014-01-01

    Considering the limited resources and the dynamic spectrum distribution in the cognitive radio sensor networks (CRSN), a half-duplex Multichannel broadcast protocol for CRSN is presented based on the home channel. This protocol maintains the networks topology only through the home channel, so there is no need for the public channel to transmit the control information and no need for the synchronization. After network initialization, node broadcasts data via home channel in half-duplex transmission way. The simulation results show that, compared with complete broadcast, the proposed protocol effectively reduces broadcast delay and overhead.

  18. Channel selection based on trust and multiarmed bandit in multiuser, multichannel cognitive radio networks.

    PubMed

    Zeng, Fanzi; Shen, Xinwang

    2014-01-01

    This paper proposes a channel selection scheme for the multiuser, multichannel cognitive radio networks. This scheme formulates the channel selection as the multiarmed bandit problem, where cognitive radio users are compared to the players and channels to the arms. By simulation negotiation we can achieve the potential reward on each channel after it is selected for transmission; then the channel with the maximum accumulated rewards is formally chosen. To further improve the performance, the trust model is proposed and combined with multi-armed bandit to address the channel selection problem. Simulation results validate the proposed scheme.

  19. Fabrication and Characterization of a Multichannel 3D Thermopile for Chip Calorimeter Applications

    PubMed Central

    Huynh, Tho Phuoc; Zhang, Yilei; Yehuda, Cohen

    2015-01-01

    Thermal sensors based on thermopiles are some of the most robust and popular temperature sensing technologies across industries and research disciplines. A chip calorimeter with a 3D thermopile layout with a large sensing area and multichannel capacity has been developed, which is highly desired for many applications requiring large reaction chambers or high throughputs, such as biofilm research, drug screening, etc. The performance of the device, including temperature sensitivity and heat power sensitivity, was evaluated. The capability to split the chip calorimeter to multiple channels was also demonstrated, which makes the chip calorimeter very flexible and powerful in many applications. PMID:25654716

  20. An oject oriented environment for multi-channel signal analysis and understanding

    SciTech Connect

    Maurer, W.J.; Dowla, F.U.

    1994-11-15

    We describe an interactive signal analysis an understanding tool for multichannel signals. The system, written entirely in the C++ language, takes full advantage of the modern workstation GUI tools and integrates traditional signal-processing methods with intelligent domain-specific tools for the exploration and analysis of semistructured problems. By semistructured problems, we mean problems that require a high degree of interactive analysis, and further, the analysis steps are highly adaptive. In other words, a finite number of rules cannot be used to obtain a good solution to the problem.